Let's say that plants really feel pain. How do we reduce that pain to a minimum? To get 1kg beef you need roughly 50kg plant matter. So eating only plants would be much more humane.

The evidence is pretty weak for plants, but even it that were true, it takes more plants to produce animal products than it does to eat plants. If we are concerned about plant death, it's happen even more for animal products

1 kg of meat requires 2.8 kg of human-edible feed for ruminants and 3.2 for monogastrics

https://www.sciencedirect.com/science/article/abs/pii/S2211912416300013

We know plants can respond to stimuli, saying they feel pain is a big jump to conclusions

Plants can feel pain the same way a machine can learn. Which means not at all outside of marketing.

In reality they simply have mechanisms to react to damage. But that's not pain.

Pain is the processing of injury in a nervous system. Plants lack the nervous system required to feel anything.

Just like a brain dead human, sponge or bacteria plants cannot feel pain in any meaningful way.

I mean, it's not really fair because plants don't have any of the same "parts" we do that would constitute a body as such. When I think of growing my body, I think of organs and tissues such as muscle, bone, blood, neurons, etc. These are primary components of what would be considered nutritional intake from a dead body that would be reconstructed for use in our own body. Plants do not have muscles, bones, etc. We are using basic nutrients like cats, proteins, and carbohydrates as building blocks for our own parts. As noted elsewhere it takes a fraction of the plant matter necessary to build our own muscles than it does to feed a pound of meat to them use to build muscle from that. So even by your flawed logic, it's still less plants to eat them directly than it is to eat meat grown from them.

Additionally, the vast majority of plant products don't even require a plant to "die" to eat. Many fruits and vegetables are just the reproductive structure of the plant, not vital for the health of the plant at all. I am an avid gardener and the only plants I can think of that have to "die" for me to eat them are root vegetables. Even then if you're diligent you could save, for example, the tops of carrots or bottom of onions to regrow.

They are completely different concepts and it's bad faith to argue otherwise.