Do you believe in gentle parenting?

Depends on what you mean by gentle parenting.
I am all for not mistreating the kids and trying to explain things in a way that they understand while still maintaining boundaries, which is my understanding of gentle, rather than being authoritative.
Permissive parenting is a completely different thing.

I was spanked as a child, so I don't believe in spanking children to punish them. I don't have kids, nor do I want them but if that ever changed I wouldn't punish my children like this. I would look for alternative ways to punish them so they can learn boundaries.