I highly doubt cheerleaders affect the popularity of Rugby at all, sure it's a bit of eye candy but people wouldn't stop going if they weren't there.
It's like the IPL when they had it down in SA. I went to almost all the matches in Durban and I found them having the cheerleaders jump up on stage for every bit of action to be damn annoying, mostly because they block your view.
Also your statement about it being only men watching is completely wrong, lots of women support rugby and you'll find tons at games.
