memes

Don't you also draw a line when you choose to eat plants?

I think there's a reasonable distinction here. You would presumably also draw a line between a conscious human and a brain dead human that won't ever be conscious again. As far as we can reasonably tell, consciousness requires a brain. Dogs and pigs have brains, so maybe we shouldn't torture and kill them on factory farms. We can also see them suffering and measure their physical reaction to it.

Of course there's a possibility that plants have some kind of consciousness too, but 1. that's speculation and 2. there's no way around farming them, as you have said yourself:

Untill humans develop the ability to photosynthesize, we are going to have to eat other species, there's no way around it.

Farming animals will always require far more plant deaths than growing plants for human consumption. These animals have to grow for months before being slaughtered and literally eat tons of animal feed in that time.

Therefore, plant-based food minimizes both animal suffering and deaths as well as plant deaths.

I'm not convinced that plant deaths are an ethical issue in of themselves, but farming has environmental implications so it makes sense to minimize the food that needs to be grown and make the farming as environmentally friendly as reasonably possible.