I think it's an excellent idea, and it's all over my FB newsfeed and gaining 60k signatures an hour, so I don't think I'm the only one.
The wording is a bit iffy - 'he should not be invited to make an official State Visit because it would cause embarrassment to Her Majesty'? One would not wish any embarrassment on one's dear Queen, but I'm sure she could weather it; he shouldn't be invited because he's a racist sexist goady hateful scumbag who shows every enthusiasm for trampling human rights. Either way, he can bugger off.
And didn't he tweet about Kate Middleton's topless photos? Part of me hopes he does come, just so she can chuck a drink on him, and then lock him in a room with Charles all night to be re-educated about climate change.