Is it a red flag?

One of my boyfriend’s best friends and recently cheated on her boyfriend when she met up with other guys on her girls trip. My boyfriend hasn’t told her boyfriend and when he told me about it he didn’t seem bothered by it. He kind of laughed about it. Most of his guy friends are cheaters as well. I don’t like how he accepts that his friends cheat and doesn't do anything about it, and how he acts like its normal. I don't want my boyfriend to be friends with cheaters. When my friend with a boyfriend said that she has a hot regular customer at work that she always hope comes in at work, we all told her to act right because shes not single anymore. My boyfriend would never have done that with his friends. I don't know if I'm overreacting or if it’s something to be worried about.