Agitation and annoyance when others don’t share one’s beliefs is the surest sign, and not from above, of a hollowness to one’s convictions. (Paul from Original Faith)
I think what you are saying can be true in some situations but not all.
There can be a legitimate reason to be angry about being presented with what one sees as a lie. To honor Truth demands this at times. Take for example someone teaching creationism as science in a public school biology class. People will get made at this and rightfully so. To respect truth demands this. I try not to do comparative religion because of this. To put the deposit of faith that I received from Christ on the same level as other religions -to be compared- just makes a mockery of the faith. It's like comparing science with alchemy from my perspective. Comparative religion in a real way makes you comparatively religious no matter what revelation you hold to.
It can just get old as well. To be told every other day, “have you taken Jesus as your personal lord and savior” can be annoying. I don't blame someone who is constantly asked this in getting mad. Sometimes one just needs respite to live ones faith without always having to question ones own premises. It's like never being able to start a race because someone is always challenging that you left before the gun went off.
When I say comparative religion I mean placing two religions on the same level. Let me give an example. I own and have read some of the Koran and the Book of Mormon. But I don’t read them in the same way I read the Bible. The Bible is the sacred word of God. It is a love letter that God has given me. God speaks to me through the Bible. By contrast when I read the Koran and the Book of Mormon it is in the context of an un-sacred un-inspired human creation. To ether lower ones revelation to the context of human creation or lift these other text up as equal to ones revelation does a great injustice to Truth and ones own faith. You can’t have your cake and eat it to. Comparative religion tries to have both and in so doing fails.
I can affirm and respect the truth that is in other traditions. I respect Muslims prayer to the one true God. I respect Mormons focus on family. I am free to respect these truths because I am grounded in my own faith tradition. These truths have there source in Christ and to pay them respect is to pay Christ respect. But I think this line of reasoning goes only one direction. You have to be first be grounded. Let me give an example of how I see this. It's like learning to play classical music as a child which can prepare her to play jazz as an adult. But flipping this around doesn't really work.