In that case [in that case, i.e. the case where chosen roleplay maps for you to a character that happens to be one that is not optimised]
to optimise [e.g. if another player starts telling you how to play, and says you have to optimise your character]
would conflict with a desire to roleplay the character. [the character that matches your desired roleplay happens to be one that is not optimised, to optimise will mean that you are not roleplaying the character that matched your desired roleplay]
A true dilemma occurs. [being forced to choose between roleplaying as you desire or optimising, i.e. changing or setting aside your desire, is a dilemma].
Ahh, finally we hit the nub of your contention. You're saying that no player should be forced to make an optimised character, because the resulting character might not match the parameters of a character
they desire to role-play.
Now, if you'd just said that in the first place, things would've been much easier. Please note that at no point did you actually talk about optimisation as something a player was being forced into, and in fact, the Stormwind Fallacy is not in any way intended to enforce such an approach. It is, and alway has been, an argument validating the desires of individual players who
want to optimise their own characters.
Note also that those who have disagreed with you have not, at any point, done so on the grounds of external pressures or limitations on character concepts - the limitations we have generally been talking about are self-imposed ones.
In other words, we have been talking at cross purposes.
Now, if I have interpreted your viewpoint correctly, then I believe it is entirely reasonable and needs no mathematical proof behind it. Any time a player finds himself forced to work within externally-applied restrictions as to what character he can create, there is a chance that those restrictions will result in him being unable to create the perfect visualisation of the character he wishes to play - which may well reduce the pleasure of his role-playing experience.
However, you seem to be countering a viewpoint which, in my experience, has rarely if ever been expressed, and certainly not on these boards. I can't recall the last time I saw someone, in the context of general discussion, suggest that you
must optimise your characters. I could imagine it being a recommendation in, say, a hardcore difficulty dungeon-delve, but that's not going to be a roleplay-heavy game in any case. I can't see it being a commonly-used restriction in any normal campaign.