Being accepting is one thing, but this is just dumb. I can't relate to what MC is thinking at all. Why would that guy be a "perfect teacher"? Did he still not figure out what that guy did? I can get not punching him in the face, since she seems fine with their history, but actively reconnecting them? This is a hentai plot if I've ever seen one.
Jealousy aside, even just for the efficiency of learning, picking someone with no emotional baggage attached is obviously a better choice.