Why have a thread about men wearing pink then? In which it is asserted that you can get away with it if you're a tough ex-army type who can face down your tormentors?
Social groups form by having differentiating characteristics, to have those characteristics strengthens your inclusion, rejecting them reduces your inclusion.
To say this thread was saying femininity is vegatice, isn't right, it's just not masculine - which is the group pertinent to the thread.
If a thread was started about some common feminine trait, I don't think anyone would assume wearing blue as a girl was negative, just not feminine. It would probably be received with some criticism as does boys wearing pink.
It's just colour of clothing, fashion might change in a few years again, who knows to what.