Both are accepted, but after a search on Google you get: 'opinion about': 1,220,000,000 results 'opinion on': 10,160,000,000 results So according to Google 'opinion on' is used about ten times more...
This really isn't a question...but if somebody said that to me i'd break up with them. You need a guy who is willing to ask your opinion and wether he cares or not, he's trying!