I was listening to Peter Jennings when he said someone asked him what the sign meant. He said Uh-hummmm! It is in the dictionary, go look it up.
I think Peter had his mind in one place since he didn't want to say what it meant.
The meaning the Iraqi's had on this sign was this
Cambridge Dictionary
wanker noun [C] UK OFFENSIVE
1 a very stupid, unpleasant or useless person, usually a man:
They're all a bunch of wankers!
Book of Slang
wankernoun 1. (Derogatory) an obnoxious or annoying person. 2. a self-indulgent or egotistical person.
I think that is a good definition for those US human shields who went over there.