Race is made up, yet racial discrimination happens all the time. Money is made up, yet we all use it every day. Just because something is “made up” doesn’t mean it isn’t real. We made it real.
Instead of a law to stop "lower" and "upper" caste from discriminating against each other (like that comment was saying), the entire concept of caste needs to be purged.
That won't happen if you continue to use those very terms and then say it's (describing) reality. The sooner people stop dealing with it, the sooner it stops being a (real) thing.
Like, who is “we”? In any situation where one group has structural advantages over another, there are going to be people who are very much not on board with merging the groups. If your plan to equalize everyone is just “pretend the groups don’t exist”, it will fail, because you’re simply ignoring a status quo that others are actively working to preserve.
There are people who want caste discrimination to exist. Given that reality, should the people who don't want caste discrimination to exist simply pretend caste doesn't exist (and therefore caste discrimination doesn't exist) or acknowledge that the former group exists and try to do something about it?