They're far from mutually exclusive concepts as they are not associated with each other, and secular humanism is a man made ideology, but someone adhering to both belief systems simultaneously may be pressurized by atheist/rationalist group-think in the secular humanist community, especially if he or she believes in their own individually constructed spiritual belief system with undertones overlapping with something like Theosophy, Neo-paganism, Hinduism, Buddhism, Taoism e.t.c.
_________________
Diagnosed with "Classical" Asperger's syndrome in 1998 (Clinical psychologist).
RAADS-R: 237/240
Aspie score: 199 out of 200
Neurotypical (non-autistic) score: 1 out of 200
Alexithymia Questionnaire: 166/185 AQ: 49/50 EQ: 9/80