My boyfriend

So my boyfriend and I have been dating for 8 months now, and I was going through his phone recently and I found him and his guy friend who is gay been texting and the gay guy likes flirting a lot with him like little comments, and emojis.My boyfriend doesn't care, but it makes me uncomfortable. I told him to stop letting him text like that and my boyfriend said he's not gay and it's no big deal cause he's just talks like that, should I let it go or bring it up again?