There are plenty of very simple examples you can imagine imagine to prove that's clearly not the case.
Men don't like being exposed to gay male sexuality in general. But between the options of a masculine gay male and a very effeminite gay male, men are far more contemptous and disgusted by the effeminite gay male. If this was really about straight men being terrified of being placed in the 'feminine' role, you would think they would show more anger towards the masculine male. But they don't.
Besides, men don't have any problem at all with women being direct and flirting with them. Quite the opposite, I think most men very much enjoy having women approach them.
You're correct about the demonization of effeminate men (not all effeminate men are gay mind you), but the issue in my mind is more about the percieved "perversion" of the masculine with the feminine. Basically: if that man can act like that, then I could be like that too! And again, because masculinity is favored over femininity in most aspects of society (everywhere where men are supposed to be and/or are the dominant force) then there is a negative reaction to that. Here are a few examples of what I'm talking about.
http://dish.andrewsu...tcalling-ctd-1/
As for the bolded part. This is true, but the same is not true for if a man were to approach a man. That is where he gets his masculinity called into question. A woman approaching a man underscores and affirms the fact that he is desirable enough to entice a potential mate, however when that mate falls into the realm of another man, then it's an abort mission type situation.