Asklemmy

Protestants came about at the same time printing and reading became more common. People came to understand the bible better. They found that their local priest or Catholic church wasn't representing the bible very well. Some priests couldn't read and were just making it up.

Catholics practice many things that go against the teachings in the bible. They worships false profits (saints, Mary, popes, etc). They practice religion with lots of ceremony and publicity. They also acted as gatekeepers to God, despite Jesus talking about having a personal relationship with God.

The Catholic church was caught out and many people were unhappy with it. So they left it in protest. Hence protestant being used to describe these new enlightenment era Christians.

A protestant would not think that leaving the Catholic church is abandoning God. They would have to see it as the right path to follow God. It's not consistent for a protestant to say they follow the teachings of Christ and the Catholic church is Christian. Any protestant saying Catholics are Christian hasn't put a great deal of thought into it. However, it would be appropriate for someone studying, categorising or discussing religions to call both Catholics and Protestant's Christians.

There is also a long history of discrimination between Catholics and Protestants. Protestants country's retained more of their own wealth and political decision making. Protestantism was more successful in places where literacy was higher. Both these factors lead to protestant countries being wealthier, more prosperous and lead to earlier and more successful industrialisation. This created the situation that many people were immigrants from Catholic countries to protestant ones. Like today, they faced discrimination. The religious difference of the incoming immigrants heightened the conflict. This also made it easier for people in both religions to see it as separate and different.