They met via work and have grown close. I asked to borrow his phone to look something up and he refused to let me which is unusual. They have a shared interest and have been meeting up with a group of others that share interest (including her husband)
Eventually he did let me look and I looked at his messages. They text multiple times daily including one message where they described each other as their "best friend"
I've obviously gotten very upset with him. He thinks I'm wrong and says "men and women can be friends"
How would you all feel about this situation?