well for one thing, the conservative slogan "defund planned parenthood" really does mean (AFAIK) remove all ways planned parenthood could possibly get a dollar from the government. it's not inconsistent to interpret "defund the police" the same way.

but more generally, it's inevitable that the opposing side will interpret a vague slogan in the most negative and scary light possible. I suspect this is often by design, ie motte and bailey: https://en.wikipedia.org/wiki/Motte-and-bailey_fallacy