I agree that we shouldn't allow negative emotions to drive our decisions but I find it quite sad and heartless when people don't see any value in empathy and compassion. I don't know how we can ever live peacefully among ourselves and other species if we don't allow positive emotions, which connect us to drive our values. But that's another topic. That's fine, let's play by your rules of debate. There are plenty of scientific reasons not to eat meat. The health and environmental benefits of a plant based diet are extensive.

BLOB_CASTLE mentioned the emission of gases exacerbating climate change. There's also the fact that growing animals for food uses way more resources than eating plants directly. This is particularly important with the growing global population. Animal foods are known to be the cause of many diseases currently affecting modern western society. Heart disease, stroke and certain cancers are some of the top deadly diseases caused by meat eating.

There you go, 3 major (non-emotional) reasons not to eat meat: health, environment, resources.