What a tragedy! First, my heart goes out to all my Dutch friends. Stay strong Nederlanders!!
Second, I lived in Amsterdam for several months last year in a mostly Turkish/Muslim neighborhood. Everyone was cool with me (as is generally the case since I tend to get along with most everyone) but when it came to my blonde Dutch girlfriends....not so much.
While there I dated 3 Dutch girls, all blondes. Each of them told me horror stories of how the Turkish and Muslim men would curse at them, throw rocks, spit at them, threaten to rape them, called them whores, basically hated on them in a threatening way. This has been going on, according to them, for years since they started letting the Muslims in.
Now, they complained, the Musims go to The Netherlands and immediately start living off the dole (the many Government subsidies) while contributing very little. Then they go and harass/attack the blonde Dutch women. It's a ticking time bomb (literally) and the attack in Ultrecht does not surprise me. In fact, I'm amazed it hasn't happened in liberal Amsterdam many times before now.