I'm at a loss..

I don't usually post on here but i'm in need of some advice. My Lo is 3 and his dad and I have been seperated for 2 years now. His dad doesn't seem to understand that he's 3 and that he doesn't understand sometimes. Don't get me wrong he has an active part in my sons life and comes over to visit him every night but when he comes over he smothers my son he doesn't want and part of it, upsetting him and causing him to lash out at his dad. His dad gets angry (which usually ends up in his dad smacking him and upsetting him more) I don't smack him and this is where we don't see eye to eye with out parenting because I think the naughty corner is more effective, but according to his dad i'm a push over.
Twice this week his dad has stormed out and told my LO to f*** off (yep that's right he told my 3 year old to f*** off) i'm at my wits end and have told him he needs to take parenting classes and now we are having a huge argument over it.
Am I over reacting???
ETA: I don't even know if this makes sense i'm just fuming angry right now!

Quoting ash_21:" I don't usually post on here but i'm in need of some advice. My Lo is 3 and his dad and I have been seperated ... [snip!] ... a huge argument over it. Am I over reacting??? ETA: I don't even know if this makes sense i'm just fuming angry right now!"

Telling a three year old to F*** off is nothing to overracted about! Especially it being his kid. Wth?!

Yeah, I know  I just don't know what to do about it and I just want him to see that it's wrong.

Oh and why im getting this off my chest he has just stated that 'He can't stand the way his son treats him sometimes' SMH he really just doesn't understand I just want to shake some sense into him (his dad that is).

  No you aren't over reacting in the least. Smacking a 3 year old and telling him to f*** off? WTF?! That is awful.   I personally would be afraid to ever leave them alone together. I wouldn't allow visits until you are sure that he is in control of himself and won't physically or emotionally harm your son again.

I know but what makes it difficult is that he really does love his dad and his dad is great most of the time.
The reply i've just got from his father is ' I don't need parenting classes i'm a great dad and a whole lot better than most' OMG