BIL's immaturity

ARGh i cant even explain how infuriated i am at my stupid BIL. first off, he's like really macho "mr tough guy" but he's such an ass. he's rude, never polite and i HATE being around him. and now, i hate him being around my son. Chace is only 5 months old and BIL shakes him around in his car seat bc he thinks its "funny". the other week, it was my husbands birthday and he had a chocolate cake. so BIL thinks its cool to hand chace the big cake, saying "OH i wanna see him grab it, its good for him". so i say NO, like twice and he finally puts the cake away. than we cut the cake, and BIL sticks his finger in his piece (oh and btw, he's 26 years old) and shows it to chace. and chace, he always opens his mouth when things head to his mouth, and i yelled NO. and BIL said, tis okay it wont hurt him. and then BIL stuck his finger in my baby's mouth. After i had repeatedly said no several times, along with my husband saying no as well, he did it anyways. and he laughed about it. its like GET A GRIP and GROW THE HECK UP. i just cant stand him. and he sits in front o my baby and says "****, chace say ****" HORRIBLE role model, and i dont want anything to do with him or my son to have anything to do with him.
how do i handle this situation,
BIL is going through depression (although i doubt it, hes just a big sissy and thinks the world owes him. i've got my reasons for thinking this) and so i feel i cant go to my MIL for this bc she's so damn overprotective of her boys and baby's them to death. HELP!!