I'm sure that is definitely the larger part of it all, yes. On some level though most men probably realise the lie.
By the "bragging that they've done exactly the same thing with a woman" part, I actually meant the tonga and bum bit.
Whenever I hear the must-be-oh-so-manly-or-I'll-have-no-sexual-credibility blokes talking about gaydom, at least one of them has to get that immortal line in there, "if anyone tried to stick their cck in me I'd lamp 'em". Yet somehow it's ok for their gf to expect it after eight pints and a curry.