I'm thinking of having a casual sexual relationship with my friend's mom
Well I'm very curious, are you thinking about it right this moment?
Yes, I think about it all the time.
While it's okay to have a casual sexual relationship, having one with a friend's mom seems like a terrible idea. If it goes wrong, it could mess up your friendship.
It's all a part of the plan. I'm doing it to make my friend jealous; I love to break up families.
You should definitely not do this if you're just looking to be a bad person and hurt others. What would you gain from this? Imagine if it were your mother who was being treated so poorly by a friend of yours and the negative emotions that this would elicit.