My kiddo's best friend is horrible.

My 4 year old goes to daycare with a little boy, "Jimmy." Jimmy is awful. He's already kind of a bully. He's rough with other kids. He's super spoiled, gets very little discipline from his parents, and is actually encouraged to be aggressive (his mom really wants him to be this alpha guy who goes out and gets/takes what he needs/wants in life). The daycare teachers have told us that in their opinion, the friendship is not good for our kiddo. Having said that there are two problems: 1. Our kiddo absolutely loves Jimmy and 2. My SO and Jimmy's mom have become really good friends.The final(ish) straw for me was a couple of weeks ago at our kid's bday bash where I was the only parent supervising the group of kids at a big indoor playground/birthday place. He was horrible. He kept pushing/scratching/hitting the other kids and every time I told him not to push/hit/scratch he just started screaming "Mommy!!! Iwant my Mommy!" He basically ruined the event because I had no time to play with/entertain the other kids because I was constantly trying to get him to stop being a bully and/or stop crying when I told him to quit being mean.I've been struggling with this for weeks because there is a part of me that just wants to say, "Hey...sorry but our kids can't hang out anymore because you guys are raising a monster." But because they go to the same day care and are good friends, and the moms are good friends...I'm really at a loss for how to proceed other than to just be the bad guy. I've brought the issue up tactfully with his mom (his dad is usually at work so I don't see him much but he is much stricter with him) but she generally brushes it aside as being normal. Is there some gentle way I could bring this up? Should I just be blunt? This might land me in hot water as it could screw up my wife's friendship with Timmy's mom. Or should I just leave it alone and hope they don't end up going to the same school? via /r/Parenting http://bit.ly/2QtKJaF