Bitcoin is a an electronic cash system. But I don't think you can really stop people from using it for other niche usecases, anymore than you can stop them from scribbling notes on physical dollar bills. Nor do I think that's a big deal. As adoption grown the bulk of it will probably be outpriced anyways.
Discussion
What if instead of scribbling li'l notes it was storing CSAM and other horrors for eternity? No biggy?
That’s already the case. See eg.: https://www.theguardian.com/technology/2018/mar/20/child-abuse-imagery-bitcoin-blockchain-illegal-content
But I don’t think the Bitcoin blockchain is very well suited for this, so I don’t expect it to be widely used for this purpose. Not now, not when Bitcoin Core 30 is released, and certainly not if and when blocks fill up and fee pressure increases.
Your lack of concern for this is alarming.