Why do so many people use such a wide brush?

With anywhere between 20,000–35,000 different Christian denominations worldwide ranging from extremely liberal to radically right wing, why do so many people try to use blanket statements for Christianity?
I myself have seen people from across the spectrum. I’ve seen left leaning, socialist Christians who have set up communes for themselves and I have also known those who are eerily similar to people I’ve seen on the news from the Westboro Baptist Church.

I personally have been scorned for my religious beliefs from people who are Christian. I just think that it’s sad that there are so many wonderful, loving, and tolerant Christians out there and they get the same treatment because of a label.