If a religion is false one would expect it to have certain self-serving characteristics. Secular humanists find that most religions have at least some these traits. Why does he care whether you worship Him, another god, or no god. A false religion would be likely to teach that God wants you to believe that religion. This prevents any freedom of thought that might allow you to consider otherwise.
Humans have a basic fear of death.
Secular humanists must come to terms with death and accept it as a part of reality. Accomplish as much as you can in this life. It's a good life. A bird in the hand is worth two in the burning bush. When the everlasting life ploy doesn't work, religion resorts to threats.