Suppose you say any system that can be used for communications must have a way to tap when a warrant is issued.
This means any encrypted communications system must have a back door built in that the government can access. And not just some single highly-regulated federal task force: any federal, state or local court in the US could in theory issue a warrant for someone's communication data, so the backdoor would have to be accessible to all of them.
Which means there's no encryption. There's no way that many separate people and agencies, all with access, would be able to maintain operational security; sooner or later it's going to blow wide open and anyone who wants to get access to someone else's communications will be able to with little effort.
That's what you're arguing for. Is that what you want to argue for?
And this is not idle abstract hypothetical slippery-sloping here. When the legal fight was happening, to try to force Apple to decrypt the San Bernardino shooter's phone, news came out that local police agencies around the country were literally lining up things like "someone was in a car crash, decrypt their phone for us so we can see if they were texting while driving" requests in anticipation of Apple being forced to decrypt phones in response to court orders. The instant you open up and force a backdoor/decrypt for one case, it will be wide open for every case, everywhere, and then we're back to effectively no encryption.