I can understand how you feel. I have a small cousin (actually second cousin) that at age 2 was a perfect horror at family dinner. He sat at the table, grabbed for everyone's water and juice glasses, drank out of each & then spewed a mouthful back into the glass. His mom & dad never said one word to him, just smiled fondly and let him continue on. After dinner he ran around "shooting" everyone with a spray bottle of water. Parents never told him to stop, his mother actually encouraged him to spray a few more people. Then he was jumping on/into a box of fruit--peaches or pears--that was sitting in the corner waiting for canning. Again, not one word of reprimand--his grandfather finally picked up the box & took it from the room. Finally his grandpa went into the bedroom & shut the door--simply to get away from this child. His mother (grandpa is her dad) then encouraged the kid to go into the bedroom & shoot grandpa with some more water. Someone else distracted the kid and he then left his grandpa alone for awhile.
I have not been back to another family dinner; I'm not especially fond of poorly behaved, ill mannered children. This child now has 2 younger siblings that I haven't even met--and don't care to, just in case they are clones of their brother in terms of bad behavior!
And yes, in this case I do consider the bad behavior to be his parents' fault. They wouldn't even try to discipline him, and if you're thinking that maybe they had tried and it had no effect & so they'd given up...I'd have to say that I think 2 would be a little young to give up on just yet, plus even if they'd given up trying they wouldn't/shouldn't have been encouraging him!