Your problem is your players' expectations of the world you're building and the game you're going to run. Killing goblins if a fundamental DnD trope/game mechanic. The world is built to make this morally justified, manageable and rewarding. There are many ways in which that worldbuilding can be changed so that "killing goblins" is no longer the straightforward go-to game mechanic it is, but you will need to make those changes clear to your players, and even then they might not realize the implications, because killing goblins is such a basic and iconic DnD game mechanic it might not occur to them the changes you made go that deep. Here are some examples of how the changes you propose could be misinterpreted by players who expect to play a standard kill-the-monsters DnD campaign:
1 - Humanoids are not evil, but my race sees them as evil. Therefore killing them is elementary role-playing.
2 - That one actually seems pretty good to me. Notice however that it is closely related to 4; it's just the gods deciding everything has a right to life instead of "good" society or the players themselves.
3 - Ecological consequences will only show up in the long-term, and they might not catch the relationship unless you make it explicit - and even if they do catch it, it wouldn't necessarily make them less likely to kill goblins; they can just handle the consequences when they happen. It might even incentivize killing goblins if the consequences give them the illusion that killing the goblins moved the plot along...
4 - The players are unlikely to introduce that concept unless they're exactly on the same page as you are and are willing to impose their view on your world. You put them in a DnD world to play a DnD game, "rights" just aren't part of the equation. It's like hoping for players to introduce communal property in a game of Monopoly. I'm sure it happens, players like to bend the games they play in many directions, but most people who play a game are going to go by its rules and conventions, and even if they want to do different they're unlikely to do it on their own unless they're happy ruining the experience for all other players that were on a different page.
I can think of an additional thing that could discourage blanket killing:
5 - Make humanoids too dangerous to attack. In this hyper-violent society where different races kill each other on sight, nobody goes out alone and nobody goes out unarmed. Just make the relevant encounters too high-level for fighting to be a viable solution. Note that this STILL requires making things explicit with the players, because they might think the point is to find smarter ways of fighting those encounters.
I think I have two general points given all this:
1) You don't want your players to kill their enemies on sight, and it sounds like it's not just a game mechanic thing for you, it's a moral/ethical/worldbuilding issue: you don't want humanoid death to be cheap in your world. But that does mean getting into "rights", either explicitly or implicitly. You are making a world where every humanoid has an intrinsic dignity and right to life, because you're the one creating it and it's how you see things. So either you create a world in which this dignity is accepted - like the gods punishing people for wanton murder, or the good societies having non-DnD moral codes of all humanoids having a right to life - or you create a world in which it isn't, but you want your player's characters to act as if it is, meaning you have to contrive a situation that will make the situation clear to them - like making them the oppressed minority whose right to life isn't acknowledged, or like another user suggested giving them quests that are specifically about standing up for other's rights. Otherwise it's a bit like inviting people to play slave-owners in the antebellum South and expecting them to spontaneously role-play as abolitionists.
2) Whatever you do, it needs to be extremely clear to your players that they aren't going to be killing people gratuitously in your campaign. Whether you straight up say that's what you're going for, or make it obvious in the presentation of the world ('After the race wars ended in an uneasy stalemate with none able to get the upper hand, peaceful trade slowly resumed, with different groups of races avoiding each other except under specific circumstances and almost never attacking each other, from fear of retaliation and more war. This made wild beasts the main danger wandering travelers had to fear...'), unless you are very certain that they are on the same page as you already as far as playstyle goes.
