// ...what reason is there, why men can't feel, identify, wear, behave, however they like- without having to pretend they are women? //
In one sense, at least, there shouldn't be a problem at all, but it's problematic to put things this way for two reasons. Firstly, you can hardly not notice the ridicule that "non-passing" trans people, particularly trans women, are subject to. That requires a change in behaviour on the part of the bullies, of course, but in the meantime it's not unreasonable to expect some people in that position to desire to attract as little attention as possible -- to, if you insist, "pretend" as convincingly as possible.
The second problem is that this seems to ignore the condition of gender dysphoria, which has nothing to do with how others perceive you but is all about how you perceive yourself. Historically, attempts to treat gender dysphoria by telling people that it's all in their head and to get over it (ie, to accept their body as it is and to match their gender to it) have been less than successful.