Not opposed if it's within the same religion. Teaching yoga to Hindus, doing cooking classes within a culture, that sort of thing. I just have difficulty when it's seizing an opportunity. I think hospital chaplaincy is a good way to illustrate my thoughts. In the old days, (50 years ago, and older) ministers had free roam in hostitals. My father, and atheist more than once had to tell some guy off to get out ... . But within your own faith, or if requested, it's not a problem at all. Baptists should be free to minister to Baptists within secular hospitals, but not free to go door to door. These days, in most developed nations, there are laws in place.
Baha'is having classes for Baha'is is fine, but disguised as 'ethics' classes when the people being ministered to already have a code of ethics,well, then, yes, I have a problem.
I've seen all the harm proselytising can do first hand. it's a subtler form of violence, splits up families, pits kids against parents, destroys existing peaceful cultures, and more. I think it should be banned outright, with the support of the UN.