Hi, im atheist and i can explain this very easily to you. From what i remember, the gospel is the part that explains jesus's preaches, correct? Well it isnt the gospel itself that makds people angry. Not at all.
The major reason why there is sort of a negative stigma around your part of religion is because of two things:
1. Particular parts of christianity's teachings are considered immoral
2. The people a part of it (this is a biggie)
The majority of the bible teaches about loving one another, and thats a good thing to enforce. However a lot of christians are hypocrites... and some use some of the bible to re-enforce their attacks on selective groups of people or to justify their actions. What do i mean? Take 1950s ish for example. There were groups of christians who believed that blacks were "filthy" and wrong and sinful. Nowadays thats redirected to gays/bi/trans people. Im not saying everyone does it, but crucial groups of people do. (South africa consists of mainly christians. The penalty for being gay is death) We understand that your bible says it's wrong, but shaming people for their sexuality isnt loving your neighbor at all. There were many beliefs in the bible that were eradicated over time.
Whats more is when anger manifests when things go against the bible. There needs to be more tolerance towards things... such as abortion or evolution or stem cell research. I picked those three because theyre very important. Abortion because the woman is in control of her body, not a religious group you have to accept that. Evolution because it's just an accepted fact (my christian friends say that god did evolution) and you cant go against a group of professionals. And stem cell research because it could be the key to replacing limbs or organs-- literally the most important study.
To shorten it up, we feel that many christians claim to always love one another and to be holy and pure, but end up being bad and cruel and using the bible for whatever they want and its wrong to us because youre such a large group of people with so much capability to do good..