“I think some of you who practice zazen [sitting meditation] here may believe in some other religion, but I do not mind. Our practice has nothing to do with some particular religious belief. And for you, there is no need to hesitate to practice our way, because it has nothing to do with Christianity or Shintoism or Hinduism. Our practice is for everyone.” — Shunryu Suzuki, Zen Mind, Beginner’s Mind.
Suzuki is not being nice here. Don’t think he’s just being welcoming or magnanimous or ecumenical. He’s stating fact, or what he considers to be fact. He’s pointing out that meditation and Buddhist concerns are not on the same plane as theistic concerns. There is no collision. Buddhism is very secular, in a way. Very much “of or relating to the worldly or temporal.”
Trungpa seems to have some concern about theism, some barely stated concern, or not even stated, but just the way he might respond to a question. He might say something along the lines of “This is a difficult matter,” and leave it at that. Or make a joke out of it that’s not quite a joke. A student might ask some long, sensitively stated question about theism and then he’ll say something like, “Theism is wrong.” And then everyone in the room bursts out laughing.