You said: Why do FT's have to feel guilty about....? I say that I think they needn't,but some do due to their unavoidable status as role models for Chinese students and/or their high morals,either or both of which they have compromised due to their natural male urges.
Of course,most Chinese expect male FT's to live like monks,foregoing the pleasures of "wine and women".But if you do that, don't instead expect to make a friend of a fellow FT of yours easily,especially if you've been in China for a long time,as you'll be distrusted by that person.
In order to avoid criticism, best to live a very boring life,maybe leading to a nervous breakdown.But then,at least you won't be berated by those FT's arrogant enough to appoint themselves as your judges!