I think it's a good idea.
It shows potential immigrants that they'll have to live by Dutch rules and laws, not the rules and laws of their home country. If they don't like it, they can stay the hell out and remain living in the crap hole they originally hail from.
wit
"...that people should not come to The Netherlands because they are fundamentalist..."
I seriously doubt an openly gay couple would be allowed to immigrate to the Middle East, so turn-around is fair play.