I looked up the etymology of "slop" and I did not find any reference to antisemitism.
So you're telling me that a word which has "slop" in its origins is itself the origin of "slop"?
This must be the first case of circular etymology!
You might object that those are really back-and-forth, but so is the claim being made here about slop. (I kind of doubt the claim though.)
I don't think your examples apply though. The dog example is just dog meaning sausage, sometimes with a temperature quality added (or ignored), but always a sausage with no other connotations.
The pepper one, maybe a little, though according to Etymonline [0] pep is short for pepper, so it's all the same really.