SR = Soft Reset (basically, saving in front of something and soft-resetting the game until it appears as a shiny). RE= Random Encounter. MM = Masuda Method (breeding with a foreign language parent to make shininess more likely). RNG = making use of the game's Random Number Generator to know when something will pop up shiny and turning on the game at the right time (there's more to it, but I'm not sure on the details.
Though you can go here to learn more.).
Anyway, as to whether the methods are "ethical" well, MM (the one you mention in the first post) was included in the game intentionally to make shiny-hunting somewhat easier. It was also, if I remember correctly, actually revealed to the public by one of the game's producers, meaning the actual game-makers intended it to be used as an alternative method.
RNG is a little more controversial, but it's perfectly legal in that it doesn't require messing with the game code or anything. It's not hacking, but whether it's "ethical" depends on who you ask. It's technically what you do by accident when you find a random encounter only you
know you're doing it instead of doing it by luck.
So I guess what I'm saying is that "shiny-hunt methods" as a whole are perfectly fine.