I honestly feel that it varies situation to situation, and it depends a lot more on personality and maturity rather than gender. Obviously, on ST, we generally see more BMs than BFs doing these sorts of things, but we're generally one demographic - people in complicated or stressful step-situations. In other situations, neither party really falls into the "only takes" category but you see less of that on here because the people in those situations won't be looking to vent. Also, us women are often far more prone to chat with friends about that sort of thing, and so the majority of our posters are females (although we do have a few wonderful male posters, as well :)). In some cases, too, I'm sure a lot of us on ST can be biased - and when we're in love with someone and someone else is causing problems, it's only human - towards the BMs motivations and/or thought processes.

As a disclaimer, I'll add that I'm not insinuating that everyone on ST is biased and the BMs are innocent, yadda yadda yadda. I don't believe that to be the case at all. I just mean it's human nature for there to be bias, especially when we love someone, and sometimes we (myself included) can overreact and overthink some things done by BMs for that reason. Most posters on ST do have legitimate concerns and problems and BMs that are absolutely out of line - but the odd time I have seen blogs or forum topics where it's been the posting SM who has been ridiculously biased and immature (no one in particular, mostly people who have come, posted one or two messages and never come back).

I guess my point there was that if you look at things like ST alone, it could definitely seem that BMs are far worse than BFs but you really do need to take other demographics into consideration, too. I've seen just as many poorly behaved BFs as I have BMs in life - my younger step-sister (she's 19 now) had a BF that could rival some of y'all's BMs, and her mom, my SM, was actually pretty great about a tough situation.