Yes, he was a secular humanist in his later years. He was a comedy genius and also musically talented. I think he did a lot of thinking about religion and how it can be used on gullible people, after his son joined a cult. He shared his thoughts in some books in the 90's.
In my twenties and thirties, I read lots of books, strengthening my secular humanism. I came across "Steve Allen on the Bible, Religion and Morality" which I still have on my bookshelf. In it he shares his thoughts on several topics from A-Z in a way to make the reader think. Maybe I'll leaf through it again today.
Also on my bookshelf is a children's tape he made with his wife Jayne Meadows called "Gullible's Travels." I don't remember if I ever played the children's tape for my kids or not, since they were already pretty well versed in not being gullible by that age. It may have been useful for some families at the time. If I ever get a cassette player again, I might listen to it, and other secular tapes I have, to see if my grandkids need to listen to it. Since they are being raised in a secular household, and have been taught critical thinking skills and fairness so very well already, I doubt they'd need to hear it.
He was very much a ''free thinker." First celebrity I ever remember speaking about his atheism! Not only that...he had the WILDEST GIGGLE!
He and his wife had a program where they imagined famous people (living/dead) at a dinner party. It was so much fun!