Hello. I am not an atheist. Who cares what soon to be fried fish think? Just enjoy how they open and close their mouths and swim around for a while.
If you saw this thing as a contradiction, you might have a problem with it, but you don't see it as a contradiction, and are a Christian in whatever way you are because you are probably least troubled with it, satisfied by what you believe, understand, and practice, and so are not seeking anything else.
You are annoyed perhaps by people being hostile towards or denigrating things you like and believe in or the way you believe in such things, so you try to make it a little better by making a response.
All you are doing is trying to feel good in a lasting way, hoping that it will lead to an everlasting good as well.
The atheist most commonly (I think likely the majority but maybe not all people identifying as atheists) do not have your hope, their life (according to what most seem to believe and state) ends when they die here and their body and organs stop functioning and they are medically dead.
You have a belief which extends you existence and gives you a hope for more good and spiritual bliss and pleasure. Even in this life, you have a friend and a helper you can turn to, talk to, and are never alone, you can even pray for things, even pray for peace in yourself.
The atheists generally do not utilize any such techniques or take advantage of such, and find it difficult to suspend their disbelief enough to actually make an effort to try such things or experience any appearance of such working.
Doesn't that sound depressing and miserable, and how you have the advantage in every way imaginable against these walking dead people?
They have no God, no belief in supernatural help or friend, they have no future really except the pitiful things of this temporary existence concluding in the loss of their bodily functions, death, and the destruction if their appearance, functionality, and bodies.
To say these things about God, or Life After Death to these people who can not really believe in such, is almost to cruelly rub it in their faces and remind them of their depressing fate and what is eventual for them according to their beliefs.
So, their only comfort, besides distraction, is to make others likewise lose their faith and hope and to make others feel the way that they themselves may feel, because misery loves company, and there might be less jealousy and hubris among equals, or so it nsy be thought.
The Atheist, hopeless as they are, want to take away your sense of advantage, and otherwise, they might wish to not hear the Sunny things that remind them of how short and futile their brief existence is.
So, why be cruel to these unfortunate minds in the mire? They have rejected the offer of eternal life in their thinking, to the point where to hear it may irritate them and burn them.