Need advice, boyfriend didn't defend me

Okay so today at Walmart me, my boyfriend and his Bestfriend were shopping for a Christmas tree. We were just looking when we found one we really liked, so we needed a cart. And all the carts were at the front of the store and we were all the way in the back in the lawn section. So there were a few stray carts in the holiday isles next to us. So I wait 5 minutes atleast and I notice this cart with just like 2 items in it was still just sitting there with no one around it, so I took it and met my boyfriend and his friend the next isle over where they were holding the big Christmas tree box. We loaded up the cart and started heading over to the food section to pick up a couple more things when all of a sudden a 50 year old Russian man walks up and pulls the cart out of my hands and immediately is hostile towards me saying I shouldn't of taken his cart and just being flat out rude, so I tell him I'm sorry and that I didn't  see anyone around that cart for awhile and he continued to be nasty. (Meanwhile my boyfriend and his friend are silent just watching and taking the Christmas tree box out of the cart) so finally I started to walk away when the man started raising his voice. As I was walking away I kept saying "byeeee" and the man yelled "go fuck yourself" at me and walked away with the cart. And my boyfriend was still silent!!! He didn't defend me or anything! My ex boyfriend would of defended me to the end of the earth over something like that. I'm 29 weeks pregnant so I just wanted to cry ☹ I was scared too. So while we continued shopping my boyfriend acted upset and "tough" but yet still didn't say one word to the guy. Needless to say I'm hurt over the situation still.. I feel like he can't protect me.. And I've lost all my sexual feelings for him.. I just look at him like a gay guy almost..like a girl. What should I do? Am I in the wrong? Is he? Help!