[Stella's mom]

We just returned from a trip with a couple that has a 10 lb male yorkie. Stella is about 5.4 lbs. The male was neutered in March and Stella was spayed in July. The problem is this, previously he just wanted to play with her but during this trip all he was interested in was her butt, she's 9 months old and didn't know what was going on and ran from him. A couple times he tried to hump my husbands arm or mine when we were holding her and of course his rocket started to pop out. Does neutering not take this behavior away? We are not pleased with this behavior but the other owners don't seem to get it. She spent alot of time on our laps because he is very muscular and we didn't want him jumping on her back. Should he still be doing this? If it is normal behavior please help me with a tactful way to handle the situation in the future
They have made the comment that we are over-protective and she is so spoiled which doesn't make sense to us. Yes, we don't want her to be injured because of carelessness but I don't think that's being overprotective, to me it's being good furbaby parents.