Hi. I am a vegetarian. The reasons are the first and third.
Let me first point out that the second reason doesn't hold. Red meat may not be that healthy, but in theory there would be nothing wrong with eating it once in a while. Still, a balanced varied diet would be enriched by fish, white meat, but also insects, but also other seafoods.
The ethical reasons not to eat animals aren't of the nature that animals are cute and nice, though it would be hard to refute the argument that we shouldn't eat animals, or mammals, because they are so related to us. I oppose growing animals in large numbers under cruel conditions then kill and slaughter them in order to make money. If you are going to eat mammals you should do it in balance with nature, be part of the food chain.
Also, if you look at the economic system around mass producing animals, it is absurd. And even in theory feeding livestock instead of yourself in order to be fed is a waste of resources. But this argument is a bit more hyprocritical if one would use it because the same inefficient and wasteful processes happen in the production of all kinds of products.
I used to eat meat all through my childhood, I liked some of them while disliking others. The idea of being a vegetarian was unknown to me and later alien to me.
Then when I got older I started both to develop views on politics, and thus also about the issues above, and I developed friendships with two persons that for some reason already were vegetarian, one male and one female, both older, smarter wiser, etc than I was and am. This defeated the prejudgement I probably had that being a vegetarian was only a thing for silly little girls that just love their furry cuddle animals (avoiding the word 'stuffed animals'). So I had three choices, either put my ideas into practice, trying to construct an argument saying that there was no problem with eating meat, or accepting to be a hypocrite.
I must say that at that time being a vegetarian wasn't that easy to do as it is now. I thought my father, who cooked dinner for me and my brother every day, would find it very strange. And I am a person who is naturally exentric and thus provoces a reaction in others, something which I, as a child, never understood or realised. Let me say that such reactions became more often positive the older I grew. But things like 'peer pressure' and the like are kind of alien to me. But still I found it hard to proclaim myself a vegetarian in the face of my father. So I just requested less meat 'for health reasons'. Then I descided not to eat any meat at all. At that time I was preparing my own meals every day. Actually, I never told my two vegetarian friends I had stopped eating meat. I guess in some way it was shameful because I admitted my 'mistake' by changing my ways.
It didn't take long to develop a disgust for meat. I do not know why this developed and I doubt it is rational. But at this time both the smell of meat being prepared and the concept of eating animals has become revolting. I think the main rational argument I can make against the taste of meat is that, compared to vegetables, it's texture is just less enjoyable. Unless a vegetable is rotten or diseased it is always enjoyable. But with meat there are always hard parts, small pieces of bone, fat, tendons, I think you will understand what I mean. That's just not enjoyable. A vegetarian dinner you can just eat eat eat. You don't have to chew off pieces from bone or do away with fat, which I always disliked.
Now I have no longer a problem with openly being a vegetarian. My family had some parties and my parents informed the family members that organised the party that I was a vegetarian so they could make sure there was vegetarian food for me. Of course family would be the least tolerant towards because you can't hand pick them. People in general, at least where I live, will make fun out of it, not in a mean way but some will say something. They make jokes while they actually respect you.
Ok I have tried this to be something informative and one should know that this my experience from my point of view. But I will admit anyway; in a sense I look down on eating meat, just as I look down on the habit of smoking. It would be a flaw in a person. I guess in a way you could say that it would be the same for someone religious looking down on someone non-religious. I don't view meat eaters as immoral, of course not. I do view being a vegetarian as a sign of being moral. Being a vegetarian isn't the pinnacle of being moral. Even when it comes to eating meat you could, for example, still eat biological producec meat (not sure if that term means the same in every country because it is a silly term).