The need for policing is not going to disappear. If we don't have trained professionals, we'll have untrained amateurs. Doubt that will be an improvement.
"Defund the police" doesn't mean taking away all police. It just means reducing funding and reducing responsibilities of the police to avoid them becoming a catch-all for any civil issue.
when in ideologically-friendly circles, you say "defund the police!" and don't worry about how literally people will take it. they will assume your position is the same as theirs and agree.
when an outsider questions you, you say "oh, of course we don't mean it literally". then you go back to using the unqualified version within your bubble. after a while, who knows what you mean? who cares?