I'd say about half of all Christians would disagree there - that's a very, very protestant look at things. Catholics believe all sins can be forgiven, as long as you truly repent. Live a life of doing good, repent your sins and be absolved though the Lord, go to Heaven. Again, over simplification, of course. "You're already an asshole and doomed unless you follow us" isn't unique to Calvinism, anyway - a variation there-of appears in quite a few other religions (Islam among them).
You've made a fair point that I did not consider Catholicism when making my previous statement, so my apologies there. However, "all sins can be forgive, as long as you truly repent" is not strictly Catholic - that is one of the fundamental underpinnings of all variants of Christianity, be it Protestant, RCC, or Orthodox. Regarding your last point, there are many, many different Protestant denominations, only a very few of which are Calvinist in nature (the main ones being Presbyterian, Reformed Christian, and Reformed Baptist). And, as far as I have experienced, none of them say "you're doomed unless you follow us." A closer (but still inaccurate) way of saying it is "you're doomed unless you follow Jesus", which may seem like nitpicking, but makes all the difference in the world.
In any case, I am not mischaracterizing christianism
Again, my sincere apologies. I did not mean to imply that any you, or anyone here, was deliberately mischaracterizing Christianity with any particular end in mind. However, I have had many conversations of this nature where I am prejudged as a Christian based upon an incomplete or incorrect understanding, so the things I say are summarily dismissed.
This is also the fundamental difference between Protestants and Catholics: Protestants view good works by Catholics as trying to "buy your way into heaven", where as Catholics view it not only as requirement to get into heaven but something you should be doing for your fellow man anyway. The other big difference is that the Protestants view the bible as the end-all, be-all of dogma while the Catholics view a lot of there ritualistic stuff (ESPECIALLY the worshiping of Saints) as required too.
#notallprotestants? Some denominations may believe that about our Catholic brothers, but most that I'm aware of don't have quite such a confrontational stance on it. I can't speak for any theology other than what I have studied (Presbyterian Church in America), but we see good works as a necessary part of the Christian faith. Reformed theology has two specific concepts regarding this, called justification and sanctification. Justification is what happens when you believe in the saving work of Jesus on the cross - your sins are imparted to him, his righteousness is imparted to you, and you can stand before God without fear. Sanctification is the process that happens after justification - the process by which the Holy Spirit works in your life to change your focus, desires, and actions. Sanctification is the process by which God builds his kingdom here on Earth. Does it mean that we are sinless, and that we know better than everyone else? Hell, no - if anything, as I've lived my life as a Christian, I've become more and more aware of just how little I know, and how broken I am in every way that I interact with everyone.
In my opinion, too many denominations (and pastors, preachers, leaders, what have you) focus way too much on justification, which is what leads to the "I've got my salvation, I know what the Bible says, and everyone else can piss off" kind of Christian (think Kim Davis, at least as she is portrayed by those both for and against her). Jesus was all about building his kingdom on Earth - taking care of, as Jesus said, "the least of these". It's a shame that so many Christians aren't likewise.
As far as Protestants regarding the Bible to be infallible, that is true. I believe scripture to be the complete and infallible word of God. However, I know myself, and therefore my
interpretation of scripture, to be very much fallible. I can just hold to the hope that as I pray, study the Bible, and live a life of faith, my understanding of God's word will grow more complete.