While I generally get annoyed by parents who don't remove a misbehaving child from a public place, church is one place I am extremely tolerant. It's nice to see parents taking their young children to church, even if the child doesn't behave properly. In a lot of areas, church-goers are mostly elderly - at least, that's the way it was where I grew up. My family attended several different churches over the years, and there was a very low ratio of families to elderly people at all of them. When I moved to the area where I live now, I was really surprised to see TONS of young people, many with young children, attending church every week - and most of the children are very well-behaved. Even when they're not, however, it's a good thing that they're there. At least their parents are trying (and trying HARD, if they're not giving in to tantrums) to raise their kids according to their religious beliefs.
Look, what's the alternative? Forbiding families to enter churches? Having a bouncer escort them out if the child misbehaves? That would just discourage families from bringing their children to church - and then you'll have fewer church members supporting the church over the course of their lives. Not to mention that fewer children would be raised according to the values of your religion - which is pretty much the point of the whole thing, right?
Look at it as a sacrifice that you're making for these children. Sure, this is your one chance a week to go to a service. I agree that it WOULD be nice if it was quiet and peaceful. But the more often your quiet reflection is disturbed by these screaming children, the more likely it is that THEY will be the ones sitting in the pew complaining about screaming kids 30 years from now. If they're taken out or their parents are discouraged from coming with their children, the kids probably won't magically become church-goers as adults. Isn't the chance that one of these screaming kids will grow up a good Christian worth a little annoyance on your part?
For the record, I don't have kids yet. I hope that when I do, I'll be able to get them to behave properly. But even if I can't, there are some places that I'd have to take them because exposure to what's there is THAT important. Church is one of those places. (My parents, by the way, pretty much bribed us to behave in church. When we were very young, we got a quarter if we behaved. When we got a little older, we had to report on a specific part of the service - generally give a summary of the gospel - to get the quarter. When we were a little older than that, we got the quarter for participating in the service the same way as the adults do. It worked like a charm, and I never noticed when they stopped giving us quarters after church.)
Vice President and Guardian of the Toilet Brush of POOP: People Offended by Offended People