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Some people have good experiences with a religion. They like it and will defend it when they hear it insulted.
Some people have bad experiences with a religion, they will insult it because it hurt them.
People come to churches with different needs. (Some churches do tons of charity work, some don't. Some people WANT a church that does tons of charity work. Some don't. Some people want a minister who really challenges them, some want to be comforted...)
UU churches are especially varied. If you like one church, you won't like all of them. If you dislike one church, you probably won't dislike all of them.
Religions are like diets. You want to talk about the one that worked for you. At the same time, you have to keep in mind that it doesn't work for everybody.
At the same time, insulting someone because something worked for them that doesn't work for you doesn't make any sense at all to me.
CC