Why ya gotta ruin it…..be a good guy

Married female here! Got a random message from an old person I graduated with. Conversation was going good all normal then boom. I get hit with some emoji’s that is like a heart face. I let it slide and change the subject. Nope this guy just keeps it up. Why do you have to do that! I thought we were having a normal adult conversation, I’m sure your fiancé would not agree with what you’re saying. So I just stopped talking and ignored it all. So frustrating! Why can’t we just not cross the line!