How would you like to live in a world where all testimony helpful to you was believed completely, all testimony harmful to you was discredited, and you were allowed to draw conclusions from the evidence favorable to you so long as there was a valid line of reasoning and permissible inferences which could lead a reasonable juror to the conclusion you were proposing? That world is called the "Charge Conference".
When the defense requests a lesser included offense, or a defense, the evidence must be viewed in the light most favorable to the defendant (see People v March, 89 AD3d 1496 [4th Dept 2011]; People v Zona, 60 AD2d 1279 [4th Dept 2009]; People v McManus, 67 NY2d 541, 549  ["The court must view the record in a light most favorable to the accused"]). We know what this means when the evidence is viewed in the light most favorable to the prosecution during a TOD motion - the court must assume that everything which helps the prosecution was believed by the jury, and everything which hurt their case was not believed.
There is a good reason for this: the jury is permitted to believe whatever they like, and disbelieve whatever they like. So for a court to take the case away from the jury, it must be convinced that even if the jury did everything they are permitted to do, they still could not reach the necessary conclusions. If the only testimony on value is $900, and the statute requires $1000, there is no testimony the jury can accept or reject which gets them to $1000. On the other hand, if someone testifies to $1001, no matter how incredible that person was, no matter how much contrary evidence there is, the proof is legally sufficient on the issue of value being over $1000.
The same test is used on lessers. If anything the jury could believe - or disbelieve - would permit them to reach the conclusion you propose, then the court must assume the jury reaches that conclusion. In fact, it is easier for the defense, because the jury need only find a reasonable doubt, not proof beyond a reasonable doubt. Disbelieving the defendant's testimony is not proof beyond a reasonable doubt (it's often treated as such, but that's a separate argument). However, disbelieving a witness is the very definition of reasonable doubt. What part of the complainant's testimony is so absolutely certain that it cannot possibly be doubted? Who invented the all-or-nothing rule, if you accept part of the complainant's testimony (to get the lesser) you must accept all of it (which proves the greater)? Where is the authority for that?
The rule for prosecutors is to ask whether any “valid line of reasoning and permissible inferences” could lead a reasonable juror to the conclusion that the defendant has been proven guilty beyond a reasonable doubt (People v Mateo, 3 NY3d 383, 409 ). That is the light most favorable to the prosecution, and there is no case saying or even implying that the light most favorable to the defense operates under a different, lesser, rule. A lesser included offense must be submitted to the jury under CPL 300.50 if 1) it is requested, and 2) “there is a reasonable view of the evidence which would support a finding that the defendant committed such lesser offense but did not commit the greater”. Do not let the “in its discretion” phrase in CPL 300.50(1) fool you. CPL 300.50(2) requires that, if the lesser is requested, the court must submit that lesser. The discretionary language deals with unrequested lessers.
The judge’s responsibility is to view the evidence in the light most favorable to the defendant, then decide whether there is such a reasonable view of the evidence. That is, to determine whether there is a “valid line of reasoning and permissible inferences” that could lead a reasonable juror to the conclusion urged by the defense. It’s the same test as a TOD motion. “When determining whether to give a charge on a claimed defense, the trial court must view the evidence in the light most favorable to the defendant. Upon defendant's request, the court must instruct the jury on the defense if it is sufficiently supported by the evidence; failure to do so may constitute reversible error. Also, it is basic that a ‘jury may accept portions of the defense and prosecution evidence or either of them’. Therefore, inconsistency in claimed defenses or even between a defendant's testimony and a defense ‘should not deprive defendant of the requested charge’ if the charge would otherwise be warranted by the evidence” (People v Butts, 72 NY2d 746, 750  [internal citations omitted]). The "jury is free to accept or reject part or all of the defense or prosecution's evidence” (People v Henderson, 41 NY2d 233, 236  [internal citation omitted]).
The way to approach this, it seems to me, is to ask what would happen if the lesser was charged, and the defendant was convicted of that lesser. Would the proof of that charge be legally insufficient? If not, then there is a reasonable view of the evidence that the defendant committed the lesser.
Step two is to ask whether that verdict - acquitting the defendant of the greater but convicting him of the lesser - would be repugnant? If not, then there is also a reasonable view of the evidence that the defendant was not guilty of the greater, though guilty of the lesser. Repugnancy is a pretty tough test to fail, "When there is a claim that repugnant jury verdicts have been rendered in response to a multiple-count indictment, a verdict as to a particular count shall be set aside only when it is inherently inconsistent when viewed in light of the elements of each crime as charged to the jury. Review of the entire record in an attempt to divine the jury's collective mental process of weighing the evidence is inappropriate." (People v Tucker, 55 NY2d 1 ). If it would not be repugnant, then definitionally there is a reasonable view of the evidence that the defendant committed the lesser but did not commit the greater.
When considering a lesser, put yourself in the shoes of an obstinate juror. You can accept half of what someone says and reject the other half. You can accept half of every sentence out of the mouth of every witness and reject the other half. You can accept odd numbered exhibits and reject even numbered ones (though not for that reason). If there is any “valid line of reasoning and permissible inferences” which could lead an obstinate (but not irrational) juror to the conclusion that your client committed the lesser but not the greater, you’re entitled to it. Jurors are permitted to believe people we all know are lying and to disbelieve people we all know are truthful. They can reject documentation, even experts, without ever explaining why.
Their role as sole judges of fact means nothing if there is no charge permitting jurors to convert those findings into a verdict.
It doesn’t matter what your theory is. It doesn’t matter that you offered proof contradicting everything necessary to a conviction of the lesser. It doesn’t matter that you would sound like an idiot arguing the lesser given everything else you’ve based your defense on. It doesn’t matter that the jury would have to thread a needle to accept this and reject that to reach your conclusion. Jurors are permitted to do that. The court must never judge the quality of the evidence. The court must never judge the competing proof. The analysis of lessers is conducted the same way as it is for sufficiency.
What part of the government's proof is absolute and irrefutable? Which witness was it who must be believed 100% if believed at all?