Would this bother you?

DH and I have been having a few little arguments lately (first year/honeymoon phase is over).

He was waiting on a response from his mother and was working on our lawn mower when it came through so he asked me to read it. So I did. But as I was backing out of it to shut down the app, a text from his best friend (female) caught my eye. Not because it was from her (I know her, they went to college together, she married with 2 kids in another state, I'm perfectly fine with their relationship), but because it was at 1 am and it said "of course! I'm always here to talk." I never bother to look at his phone normally, I trust him completely as far as cheating and the like goes. But... I opened the thread and read it.

He texted her while he was at work (24 hr shifts) at 9 pm, just chatting at first, (he said he couldn't wait for hunting to start so he could escape, and she responded with "haha too many people everywhere now"?... It's just my daughter and I and she hangs out in her room a lot playing and almost always busy cleaning or helping her so...).

But a little later he said they needed to talk soon, and she asked what was going on. He told her about our arguments. Not in great detail, but enough, basically saying that the little things kept adding up, and then we get pissed at each other and argue, and after we argue, we talk and everything is good, but it happens again. And then stated that he always feels like he's always extending the olive branch, which is not true, it's about 50/50. And that he always feels like it's my daughter and I against him. Again not true, he's been a father to her for about 2 years... While I've been on my own with her for 8 before him, he's tends to pick at her sometimes and I don't stand for it.

This friend told him it's the little things that make or break a relationship, and that we needed to decide if this is what we want and if not, end it. She also stated that I should be on his side and not my child's. Everything she said was polite enough... The conversation ended at 1 am.

I didn't tell him I had read it. I was too angry and hurt. Then I was kind of ok with it, i would never tell friends about our arguments, but maybe it helps him deal. But I keep thinking about it, and I just still feel violated? Disrespected? I don't know, how would you feel about this? What would you do? Thanks! Sorry it's so long!