I guess as long as everyone lives by the "do unto others as you want done unto yourself", there wouldn't be a problem to anyone. This would include animals!
Probably more than you realise. We all kill - we have to to live this is part of being alive: Death beggets life. Whether it be plant or animal, we kill. The question is whether we murder, and in asking that, we must define what murder is.
Well firstly I disagree on the worst crime, according to the law the worst crime is treason, according to me the worst crime is rape (and sadly it's extremely common ). Most importantly though, I think we're at that point of defining what murder is again.
Now as a concept most people seem to think of murders as people who kill for sport. In reality this is very rare, it is the domain of serial killers. Murder however, usually happens out of revenge. To me murdering for revenge is a tough thing to stomach, I am morally impartial to the act of the kill, I just dont think revenge is ever a good motive.
However, i'd have no problem with murdering a rapist if I believed there was sufficient cause to believe they would rape again. Thus, in my own moral code I have no problem with pre-emptively murdering a guilty man from repeating what I see as the worst crime. This is not something I struggle to justify within myself.
Defining what constitutes a murder goes wider, in my view, than specifying which species was killed and determining that the kill was not accidental (manslaughter) or within reasonable force (self defence).
To me murder is the act of killing for revenge.
Also to me, I do not see murder as a terrible crime, because let's face it, if somebody is killed in an act of revenge then there is fairly good odds that they deserved it. Of course that's not always the case, murder can be an over-reaction, in which case it's sick - but if somebody was to murder a rapist out of revenge then I'd not bat an eyelid.
Of course killing for sport or financial gain is just plain wrong, but the serial killers and Harold Shipmans of this world are thankfully a rare bread, and not what i'm discussing here.
You put an animal down because it is ill enough that it will suffer even more if it is kept alive. When you kill an animal to eat it, it is perfectly healthy. What if people just killed their dog because they didn't want it any more, but they did it via injection.
It's known as a genetic memory (or meme I believe). It's a purely instinctive reaction to the genes that have been passed on to it by the whole process of evolution. A classic example being: Some birds learn to migrate in summer as those that did were more likely to survive and pass on their genes so this instinctive reaction is passed on to the next generation.
Define mental torture. I was very careful to use the term "pure mental torture", by which I mean no changes in physical environment. To the best of my knowlege any life form incapable of self awareness can not possibly suffer from pure mental torture. It can only react to a restriction in it's instinctive behaviour. Which is exactly what animals do suffer when caged for example. Despite not being harmed in any other way, they suffer from mental anguish due to the simple fact that their instinct is telling them to behave a certain way and their environment is restricting them from being able to do so.
For example: Put a bear in a cage and it will become "unhappy" if the cage is small and it can't wander around and act in other instintive ways. However, make the cage big enough and fill it with trees and various other things and the bear will be perfectly "happy" there and not show any of the symptoms of mental anguish, (breeding is a very good indicator of an animals sense of "well being"). This is a fact, despite the fact that the cage may well actually be incredibly small in comparison with the natural "territory" such a bear may well have in the wild. BUT, put a human being in a cage and no matter how you dress it up and add things to keep the human "happy" they will always know they are imprisoned and so will suffer mental anguish, (and that's despite the fact that as animals our territories would be far smaller in the wild than that of a bear). This is a critical difference between humans and animals such as bears, and it is down to one thing and that is the sense of self consciousness.
ehh?? By definition it is suffering that makes it pain !. If there were no suffering it would be just another sense.
Actually I provided perfectly adequate evidence of what I stated.
Migration is not a 'genetic memory', birds will migrate if they live in an area which is cold enough. E.g. the very same bird, the blackbird, is a migrator in Sweden and not in Italy Even migration paths are learned and transmitted from generation to generation.
Birds (and many other animals) usually adopt a 'best practice' approach which means good behaviors can spread into the population inside the same generation, no need to call genetics in - though that may explain why some individuals are more 'creative' in finding new good behaviors while others are less so inclined.
The less 'creative' inclined subjects can be mistaken for less intelligent, since there's generally a lack of reliable metrics to assess intelligence.
As for instinct vs intelligence it's a debate I wouldn't touch with a 10 ft pole, e.g. I could say love for one's children is a preprogrammed response (=instinct), which is of course partly true, but also hits the mind as a gross overstatement.