thats a very open ended statement isn't it?? There are lots of straight guys who love big breasts as well as many liking smaller 'handful' breasts. For some guys they may not be the most interesting thing about the woman they're with?
being gay 'breasts' do nothing for me sexually at all, if thats what your mate's talking about, but do they fascinate me, a little bit but more from a 'do they get in the way when you sleep' 'where do they go when you lay down' etc.
I don't think i know any gay guys though who are actually 'into' womens' breasts, so why does you mate believe 'all men likes tits its a fact'??? Generalisations are rarely 'facts'!!