That's not even one of Uglúk's faults

[The Might]

In case Tolkien didn't really make all up then that might be our source of vampire legends and other strange sightings.

They might be in the sewers of our great cities right now planning how to get back at us.

Actually, it is quite interesting to see how they are presented in different works.
In The Silmarillion as well as in The Hobbit they are presented as evil creatures with seemingly no possibility of becoming good.

Now goblins are cruel, wicked, and bad-hearted.

Also there are no examples of them showing any sign of kindness in these books as far as I am aware.

Whereas in LotR there are these few examples. From the discussion between Shagrat and Gorbag one can see that they could be friends (at least until they fight over something) as they planned living somewhere away from any masters to command them.