I am disgusted by the attack on the Bath Mosque (and by all crime, whatever its motives). The point about why this has caused outrage is not because the victims were practitioners of religion, but because when you are in a church or a mosque, the doors are left open for people to come in, so they are peculiarly vulnerable to attack. It's a violation of trust.
Also, I don't like the idea of something that is sacred to someone else being desecrated (whether or not I find it to be sacred). Add to that the fact that moderate Muslims are under attack from both the general public, who tar all Muslims with the brush of extremism, AND from the extremists for being too moderate, and you can imagine how isolated and vulnerable this sort of thing would make them feel.
Also I am saddened that this sort of incident undermines the efforts made by people of all faiths and none to live peaceably together in mutual respect and understanding. If someone came into my house and urinated in my sacred space, I'd feel very vulnerable and frightened.