liz took the words out of my mouth. When a woman complains, men try to fix the problem or get the woman to settle down. When she doesn't, they get frustrated and even feel like they're not doing their "job." And they get offended that the woman is not following their helpful responses.
Yes, a heads up that venting is going to occur would help the situation. Or talk to another woman about it. We listen more, make sympathetic noises, and agree that the guilty soul is "insensitive, a *****,.....or whatever!"
And talking to your boyfriend about the difference between venting and really needing his help is a good idea.