JRZ - how odd, anal sex was what popped to my mind when reading the OP as well. So let's take a guy who enjoys something up his butt so much that he thinks its ok to hold her down, as she tells him to stop, and shove something up her butt. Ummm.... hello??

Physically forcing anything on anybody, as they are telling you to stop, is wrong. Period. No excuses for anybody.