Personally, I'm agnostic. I don't really care about if there's a supreme being or not, all that matters is that you are a good person overall. Coming from a family with a Muslim father and a Roman Catholic mother, I've come to tolerate and respect religions of other people, as long as they respect my lack thereof. Also, if I disagree with someone's religion, I come up with a reason for it, not just because it's different from my views.
Unfortunately, not everyone has the same tolerance for others, primarily American Christians. These people live in a bubble of ignorance, and really can't seem to have any respect for anyone other than American Christians. This, of course, doesn't apply to everyone, but an overwhelming majority. I'll give two reasons why I can't stand Christians in general:
1) They don't know about/care about any religion other than their own
This is a huge reason as to why I don't like to talk about religion to anyone in person. It's because none of them know what the hell they're talking about, unless it's on bragging about Jesus Christ.
For example, I was talking to my friend and I mentioned that my dad is Arabic (He was born in Syria) and that he is Muslim. My friend responds, "Wow, he's Muslim? Does he know any terrorists?". Nothing about the 5 Pillars of Islam, nothing about Ramadan, which is a one-month fasting period, nothing about the Qur'an. Just terrorists, and then he followed up with, "Does your mom wear that towel thing on her head?". Some people are extremely insensitive.
2) They try to cram Christianity down your throat
I dare my friends to try and teach me about Christianity. I've read the Bible, the Torah (English, not Hebrew), the Vedas (English, not Hindi), and the Qur'an (English, not Arabic), so I think that I know a little bit about most popular religions. I try and focus most of my efforts on Christianity so I can tell whether or not what my friends/any Christian says is bullshit or not.
One of my friends said, "Christianity is a religion of peace and non-violence!". I quoted Leviticus until he realized that it was the exact opposite. I school Jehovah's Witnesses when they come to my door. People need to understand that they can't fool people all the time, they need to be honest with people if they need to convert.