This would be unacceptable imo.

He chose his friend getting laid over you, your feelings and your comfort. He chose to lie FOR HOURS and maybe more (because they agreed to meet a group of "hot girls").

Also, his friend doesn't seem to have problems getting laid since that is what caused the end of his relationship.

For all you know his friend could be lying too, he is a known liar and cheater. And your bf sees nothing wrong with it and followed his lead in lying, who's to say he didn't do the same with cheating? Why would you believe his friend or him?