I think for anybody to discount the effects of gear on mood and behavior would be to totally ignore the evidence. It's like saying somebody with gyno just didn't take the proper precautions. It's b.s. to say that if you get roid-rage you were an asshole before gear. It might be true, but it denies there might be a problem. The evidence is clearly in favor that hormones affect mood, and the fact that we are injecting gobs of exogenous hormones it only stands to reason that there might be mood swings.
Does this mean that it will happen to everybody? No, it's kind of similar to gyno again, some people are more prone than others.
I also think certain gear is worse than others. Test for instance tends to make most people almost euphoric, deca and ox seem to have little to no affect on mood.
But the main offenders I've seen/hear/experienced are tren, Winstrol (winny), and dbol. And in fact (I think ulter pointed this out if I remember correctly) some have added test to their tren cycles and seen their anger and irritation lowered.