MIL has herpes

So my MIL was very recently diagnosed with herpes type 1 and 2

I am 19 weeks pregnant, my boyfriend told her that she can't kiss the baby because of the herpes (I thought that was common sense though)

So MIL went on the phone with my sister in law crying about what my boyfriend had said so then, sister in law texts him calling him an asshole saying he shouldn't have said that, and that he was only saying it to be mean. I'm very upset that they aren't seeing the bigger picture, that he's not saying it to be mean. I don't know what to do, I feel like I should step in and apologize but I don't know how I would do that.

Update: Sister in law said that we are ignorant for saying she can't kiss the baby because herpes isn't contagious unless there's an outbreak or a flare up, I always thought it was contagious no matter what but more contagious if there's an outbreak, do any of you know if her statement is true or are we really just ignorant?