I know exactly what you mean Wendiwoo. Everyone's situation is different so I don't know if my experiences will be relevant though but, for what it's worth: In the past if I ever complained about this, the answer was 'Can't you take a joke?', i.e. it was my fault for being too sensitive. I probably was too sensitive (but, whatever, this sort of behaviour has nothing to do with humour as putting someone down is not the least bit funny).
I hate it when I see other men put down their wives/partners in company; they don't seem to realise that it makes them look pathetic, not their partners. Once I took this on board myself, I could actually see what my husband looked like to others if he put me down (or, the other annoying habit, talked over me as if what I had to say was never of any importance). Now, because I go out with friends a lot more and feel more confident and comfortable in myself (maybe just getting older/slightly wiser/less concerned with what others think), my husband doesn't belittle me nearly as much and, if he does, I just don't care and, if you don't get a reaction, not much point doing it! And so it happens less and less now and our relationship is much better for it.