this is such a messy topic for me - not really sure how i feel!
because all aquarium fish were captured at some point, so it would be in some ways contradicting to be 100% against it. it has also helped the longevity of species that are nearly extinct in the wild such as Endlers and Cherry Barbs.
However I don't like taking wild fish that could easily be bred in captivity, or fish that are endangered. I'm also not a big fan of keeping fish that have to be wild caught because if they can't reproduce in captivity, then they probably shouldn't be kept in small tanks. This is part of the reason why I haven't gotten into SW fish yet ...