You can objectively argument that nothing can be known with 100% certainty by simply stating the fact that there are many things unknown, and if any of these things are related to it, you wouldn't know it 100%. So the only way to have certainty in your knowledge is omniscience.

That said, there are so many facts evidentiating some things that you can treat them with a certain level of objectivity, but still aware of the fact that you don't fully know them.

Indeed, we're not the same. We're a lot closer to the mammals than we are to the trees and vegetables. The truth is that we're so different that we don't know much about trees, but mammals are really close to us, we can easily bond with them.

We're still researching about everything basically, and even about the things that we think we already discovered 100%, there may be something we don't know yet. We recently discovered that trees got a close community and can communicate with each other, you should research about it. So we should value everything that's alive.

If it is the killing itself, then you vegans have that problem of killing life. Plants are life. — Harry Hindu

Yes, this is a problem for most living beings in this planet, we can't go on without killing something else. But this relation with fruits at least isn't that bad, the tree is giving the fruit for anyone that wants to eat it, so they defecate their seeds and proliferate their species.

Maybe eventually we will find a way to live without having to kill other living beings, i think we could do it by absorbing the elements we need in it's raw form, the same way plants do it. But right now this is out of our reality, we need to focus on what we can do with what we got.

Let's tell the truth folks. We are animals. Being an animal means being controlled by your instincts. But we are the only animal that got the potential to stop being an animal, we can gain total control over all of our instincts.

Our animal instinct controls our conscience, it compels us to eat meat. This drive we got to eat meat is so strong, that we unconsciously try to find reasons to be moral while doing something immoral, to blind ourselves to the fact that it is wrong to cause pain and cage another living being, though even a child can recognize this. This is the conlfict between moral awakened conscious and wild neutral instinct.

130 years ago, slavery was legal in my country, Brazil. My great-grandfather was a slave, but I'm white. Today, we all perceive slavery as completely immoral. The instinct to profit on top of another is not as basic and primitive as the instinct of eating meat. I've got faith that eventually, we will stop doing everything that is immoral and we will stop trying to see things that are immoral as moral.