Historically “humanism” is a philosophical position that values human life, needs, freedom of choice, humane action, and relying on empirical evidence rather than dogma to decide things. In our time the term has become conflated with “secular humanism,” which technically is the humanist position that excludes God from the human equation.
For many conservatives, this version of secular humanism, in particular, is a pernicious evil that needs to be guarded against. These conservatives believe that proponents of secular humanism actively seek to displace anything connected to the divine. In this view, people who identify as secular humanists look down on those who want to include faith and the divine as an important part of life. They seem to believe that such conservatives are basing their views on superstition instead of reason and evidence.