Something like "De-thugify the police!" (or "No thug cops!", or "Get rid of dumb cops!") might've worked better ("Reform the police" is so bland that it might not excite anyone), and TBH they could've gained a lot of support after that school shooting where the cops just stood around being stupid for an hour or so (I forget which city it was, you know one of the ones of several that occured recently).
In that linked article a congresswoman explained that the phrase meant "It's not a slogan but a policy demand. And centering the demand for equitable investments and budgets for communities across the country gets us progress and safety.". But come the frakk on, if you start with "Defund the police", people who disagree with you will have stopped listening before you continue with "... and by that I mean...".