The thing that's important for most people who belong to any church is their own personal connection to that church through their own personal history....and that is where their affection for the church stems from. If their own experiences in the church have been, for them, positive ones...then they will see the church in a positive light.

When they are defending the church, they are not so much defending its doctrines or its dogma in most cases as they are simply defending their own past.

Having said that, many Catholics are kind and compassionate people who DO good in the world...regardless of the abuses that have been committed by the Catholic Church.

It works much the same way with patriotism to a nation...even when that nation commits wrongs against other nations. People naturally will defend the various cultural foundations they grew up standing upon.