What a braindead argument. Sometimes bad things happen to human children so we can excuse animal cruelty on an industrial scale.
And it's not just the separation, 99% of male calves are killed immediately after being born, while females are either filled with hormones so they can be grown for meat, or they are raped year after year so they keep producing milk.
To gain what, exactly?
Is it really that hard for you to accept that some principled people may be genuinely against something that you tolerate?
You're seeing more of it recently because veganism is actually on the rise, both because awareness about speciesism is rising and because of climate concerns. Plus you're on the fediverse, where the concentration of principled radical leftists is higher than other platforms.
And is this one of those idiotic things? Are you implying trying to reduce animal cruelty in the world is idiotic?