Its controversial because people tend to have a black & white view on things and the truth about it is in shades of grey.
There are leafs that might be good idea to remove, rarely is a heavy defoliation a good idea imo, but sometimes it might be. There are various reasons to remove a leaf, but more reasons not to remove one. If you dont know if a leaf is ok to be removed or not, then you should not be randomly removing leafs.
Some of the principles in removing leafs is that if you remove it, the light it would catch ABSOLUTELY MUST be catched by another leaf close to it. If you remove a leaf, the budsite growing from it must be big enough to be able to take care of itself and get enough light to grow. If a leaf is not getting any light and is just in a bottom of a bushy plant preventing air circulation, then its a good idea to defoliate a bit from down stairs, and also remove any budsites from them, because they wouldnt grow big either due to lack of light down the plant. If you can tuck a leaf to stop it from shading, its much better, especially in vegging. During flowering tucking tons of leafs might cause it to be too humid and cause bud rot. blablabla
TLDR; if you dont know what you are doing, dont do it!