Relationship advice needed

Ok, so I personally am in a bit of a jam - I'm currently unemployed due to a series of events which would be otiose to reiterate. (Not that it matters, I just wanted to use that sentence)

During my enforced period of stasis I have become aware of the most toxic, one-sided relationship I have ever seen - A barely employed male with the most disturbing hand shake - (no, not Japanese Mr Hand Shaky Man), and general stanky b.o., and this dude (yes, I know that's terrible grammar)Is about to marry an old friend (chick, 4 boys already) and has somehow managed to produce a kid (girl ,addhd) already.

The older boys have already threatened this dude with a beat-down if he proceeds, but it seems the threats fall upon deaf ears.

When a 45+ year old man screams blue murder at an innocent 4 year old girl, what do you do? It's his kid - he has the right? I don't know. My heart tells me to pick up a plank of wood and smack the fucker in the head, but I just don't know.

Any thoughts would be appreciated. :-)