It's a fashion statement for some people I've found. Like the Anarchy symbol on a T-Shirt. I've run in to people with such a hard line opinion on the matter who couldn't even point to where Palestine is a on a map.

At least in the US I can guarantee you that the % of hardline pro-Israel people who can actually point to Israel on the map is at least twice as low. I'm willing to bet my assets on that.