Men and women who spend a lot of time alone together (or just having private conversations on Facebook or at a bar or a restaurant) are likely to cross the line from just being friends to more.
Therefore, in my view it is a bad idea generally for someone to go for drinks or lunch with a married member of the opposite sex or simply to engage in frequent private conversations with the person.
(I can see many exceptions to my principle. If you are doing a business deal and some socializing is required, OK. If you guys have been friends for a long time, I see nothing wrong with occasionally getting together for drinks or a meal or a FB chat, but it is dangerous to a marriage. The more private time you spend with an attractive member of the opposite sex, the more you endanger your marriage.)
I was asked by a 20-something single female friend about if there was anything wrong with her taking up a married guy’s offer to have drinks.
I said yes. She said, ‘But he has a bad marriage and he’s suffering.”
I said, let him go have drinks with his male friends. She said, he said he didn’t have male friends.
I said, this guy is bad news. Stay far away.