all that cartoonist's work is ugly, Rosetta; I don't like him at all.
However.
I didn't know Sharp was Jewish, and I wouldn't have been any the wiser if I'd seen the cartoon. According to the BBC, the cartoon showed him with "exaggerated feaatures". Well, that's what cartoonists do, all the time. I thought maybe he'd given the figure the sort of huge nose that used to appear in Nazi cartoons; but not at all here.
A far as I can see the only thing that might conceivably be seen as anti-Semitic is the notion that Jews make money and run things, though even that is a nod to success, not to prejudice. The cartoon is plainly anti-Boris but I can see nothing offensive at all in the depiction of Sharp. The Guardian should have stood its ground.