You give yourself much undeserved credit.
Pride is a sin.
So, is presumption.
Well, at least you didn’t copy-paste a screed from www.ihatelutheranswithahothothate.com.org this time.
Yes, presumption is a sin, and Roman Catholicism is guilty of it. Presumption is trying to put yourself in God’s place and take God’s judgment from him.
And the Lord has said that we can have assurance from him of our salvation. That’s his judgement.
Roman Catholicism, however, is eager to call God a liar and undo his judgements.