You are free to believe what you believe but there is a line between belief and getting in people's faces and condemning them to hell.
There are Christians who are bent on telling non-Christians that they are doomed without Jesus.
Am I offended by Islam? Yes. Am I offended by Christianity? No. Just the “we're right and you're wrong” Christians who make every attempt under the sun to convert Jews to Christianity. And Thank G-d these attempts haven't been very successful.When a Jew abandons Judaism he/she has committed a terrible sin. At least Judaism doesn't claim to be the only truth. Ours is not the only way to G-d. All the righteous have a place in the World to Come.
So I gather you are offended not so much by what these people believe, but rather by the rude way in which they present their beliefs. That makes good sense.
FWIW, most of these people are at least equally rude when talking to other Christians, condemning them to hell for rather minor differences in doctrine.
My personal belief, and I hope you don't find it offensive, is that the vast majority of people will in the fullness of time be saved by Christ. I don't claim to have any idea how this will be accomplished, but I believe that only those who stubbornly refuse to accept the obvious truth when presented to them will remain eternally isolated from God.
IOW, it's their rejection of God, not His rejection of them, that dooms them to hell.
You mileage, of course, may vary.