I've always found "Protestant" to be a rather ugly word. It does a huge disservice to the faith, and in some ways legitimises Catholicism. Christianity, by its very definition, is not about what we don't believe, but what we do. In evangelism and apologetics, it is very rare for me to mention, or even allude to Catholicism. The obvious exception is when Catholicism provides a barrier. If I'm trying to witness to a Catholic, of course I'm going to oppose Catholicism. Similarly, if an unbeliever attacks Christianity on the basis of Catholicism, I'm going to explain the differences.
However, when Catholicism is absent from the target's mind, it is also absent from my own. The message a Christian brings is simple: Mankind has sinned against our Creator, and is therefore worthy of His wrath. However, in His love, God instead chose to send Jesus, His Son, to live a sinless life as a man, die on a cross on our behalf, and rise again so that through faith in His death, resurrection and Lordship, we can have a restored relationship with God and inherit eternal life in His Kingdom when this life is over.
The above is obviously a very simplified version of the Gospel, but that's what it is. But the term "Protestant" makes it sound like the Gospel is actually "reject the authority of the Pope, refuse to venerate Mary, cease to observe the 7 sacraments in the manner of the Catholic Church, and disregard their traditions". But that's not what it's about at all!
Through the mere fact that Christianity is a positive belief in the truths presented in the Bible, it ceases to be a negative belief in the Catholic Church. Christianity existed before there was a Catholic Church to protest against, so it's hardly fair to call us Protestants. Now, by its nature, Christianity is very much "protestant" of the Catholic Church, in much the same way as it is "protestant" of Mormonism, Islam, Evolution and all the other religions that teach anything different than the Bible. Truth, by its very nature, is opposed to all lies. However, truth is independent of those lies. Truth is not defined by its rejection of lies, but rather is self-sufficient.
As a child, I received many negative marks on my maths homework. It never was my strong suit. I'm still terrible at it now. But for every sum I got wrong, there is a right answer. Now, I do not have a specific example in front of me. It's been a long time since I was in school, so I doubt any of my old homework even still exists. But let's imagine I incorrectly guessed 7 x 2 = 17. It would be ridiculous to define 14 by the fact that it is not 17. 17 is the wrong answer, but 14 is the self-sufficient correct answer. But 14 is naturally opposed to 17.
In the same way, Christianity is not defined by its natural opposition to Catholicism, but by the fact it is true. It is the religion defined by the very word of God, and even gives itself the name "Christian" in no less than three places. The errors of the Catholic Church have no bearing on the sound doctrine that finds its origins in God's word. Thus, the word "Protestant" is, at best, redundant, and at worst as daft as calling Christians atheists because we don't believe in Allah.