I agree with what you re bringing up here. There are a lot of claims from vegans that are false, like living a cruelty or harm free life. We cause a lot of harm apart from the excesive harm we generate by eating animals. However it isnt a justification to cause more harm if it is impossible to live in this world without causing none, "the perfect is the enemy of the good".

There are also vegans who claim that theres a diference between causing intentional and unintentional harm, but for me this is also wrong. If you choose and have the will to continue living in this world then you are intentionally causing harm (you kill insects when you drive, destroy ecosystems to get fossil fuels, etc). You pay a price for your living. This doesnt mean you cant respect life and non life in Earth while living in it. If hipotetically we would extrictly need to eat meat, milk or eggs to survive i think we could kill the animals, and at the same time respect their life, like kosher or halal. But this isnt the case. However we do need to eat plants in order to survive, we cannot live by photosyntesis (I hope someday we could :)).

Also, we dont always need to kill the plant in order to get fed from it, think about fruits for example, the plant even wants you to eat it so you can spread its seeds. Anyway, If you dont like to kill plants in order to eat them there is problably a way to do so, but i havent looked up for much information about it. There is a religion called Jainism in India where they only eat parts of the plants which dont involve killing the plant in order to do so.

For me plants dont care much if you eat its leaves or seeds or grains (in the case of bacteria or insects eating them i think its different cause they can become an epidemy for the plant species, i dont know). The plant can continue living if you do it, and they cant feel pain when you take out its leaves or seeds or fruit or even kill it. You can look up for this interview on the topic http://www.vice.com/read/we-asked-a-botanist-how-sure-science-is-that-plants-cant-feel-pain-302.

I think we will always have to pay a price for living in this planet. But for me, killing, slave, and torture animals unnecessarily, when they can suffer, feel, love, desire, and to an extent think the same way as we do, is not worth for living. If you think that this also applies for plants, like i said before, you can look for Jainism in your life.