many of the people who make this kind of argument are themselves in favour of e.g. harsher sentencing for offenders, but that without their wanting to house felons in the newly converted basements/secure-units of their own homes. Or are in favour of stronger national defence without themselves joining the territorial army. And I see no problem with that. There's no tension between my wanting that the government do something and my being disinclined to act privately to secure that goal. I don't myself fix potholes in the road or repair streetlights, but I hope I'm not a hypocrite for wanting that the council do that.
What are the downsides?