I don't think an atheist can be strong in their faith since the definition of an atheist is to not believe in any Gods. Faith is believing in something. How can you believe in not believing or be strong in it? For me, I used to care what people believed, but that was a long time ago. Life is much better letting people believe what they will, share what I believe if there is a relationship and willingness to receive. If not, shake the dust off and move on.