My bf loves grabbing my bum alot in public, is that embarrasing?

what he does most of the time is smack my bum then grab it and then slide it down towards my crotch,like in between my thighs from the back, if you know what i mean, its quite a dirty grab, i like when he does it and it turns me on but he does it in public, should i be embarrassed, what do you guys think, what would you do if you bf/gf did that to you in public.i did ask him why he does that when im with him, he replies that he likes the size of my bum and that its really cute.