You want my two cents on that, you will find it tied in the origins of the Hebrew religion.

Josephus I think recounts how around when the sons of Jacob were in Egypt, one was "favored by the priests of Sebek".

You also have the serpent depicted as the source of temptation in Genesis.

Now, Hebrew doesn't have different words for "legless repitle" or snake, and "legged reptile" or serpent. It does however have a separate word for crocodile, although when this came into use isn't clear.

So, maybe it's a historic throwback to the early Hebrews being offered gifts early on a project that turned into a big pile of poop, namely going into Egypt for famine relief and then being enslaved and oppressed.

Hence the stigma. "These are the sort of people that will be happy to welcome you and also happy to see you enslaved".

David Icke was big on Evangelism early on, he certainly got a good whiff of that literary nerve gas.