Transcribing the conversation here:

Recessa, ↑4 ↓1: That's completely idiotic, milk exist because there's demand for it.

commie, ↑1 ↓4: I think you understand that milk is produced as part of the mammalian reproductive cycle. can you describe the causal steps between demanding milk and it's production?

friendlymessage, ↑3 ↓2: Do you think dairy cattle just randomly spawns on the planetary surface?

commie, ↑1 ↓3: do you think there's a direct causal link between drinking milk and more being produced?

friendlymessage, ↑3: Are you fucking with me?

commie, ↑2 ↓3: no. I'm trying to illustrate that markets are not governed by natural law; they are populated by irrational actors.

friendlymessage, ↑2 ↓1: Yeah, but they're not as irrational as you are and producing milk costs money. If there's no market, they will stop because they are not fuckin lunatics and they don't have infinite resources

commie, ↑2 ↓2: milk was farmed before markets existed. there is no reason to believe that will ever stop.

friendlymessage, ↑3 ↓1: That... must be the dumbest discussion I've had in a while. Please read through your comments tomorrow when you're sober

commie, ↑1 ↓1: I've been sober all day.

friendlymessage, ↑1: Okay, whatever you say

commie, ↑1 ↓2: everything I've said is true. you're objecting to reality, and being pretty shitty about it to me.

friendlymessage, ↑2: No, you're just making a no sensical argument at all. Milk was farmed from dairy cattle because it was consumed by humans. It's simple supply and demand. There is no rational argument at all that if mankind stopped consuming milk, it would still be farmed. Why would any farmer go through the effort to upkeep cows and keep them impregnanted to make them produce milk if they cannot trade it or won't consume it? Yes, humans have free will but they won't produce stuff with very high effort just for fun. Except maybe very sick minds that just enjoy animal cruelty. And you won't elaborate what your actual point is anyway.

Also, not that it matters, but you're arguing that dairy farming existed before the market is simply wrong. There has been trade between human civilizations long before we started domesticating animals.