I'd trust any democratic government doing a preventative security scan for vulnerable devices, over some hacker who's only out to exploit them for personal gain.
Most people have never patched their router nor even know how to. Someone needs to proactively inform that group that they're vulnerable, at scale, if we're even going to have a chance to solve a lot of network problems.
It depends on what kind of actions they wish to do with the resulting scan/hack.
If they offer services to secure people/companies free or cheaply, then its a overall large positive.
If they give it to their equivalent NSA apparatus, that's a major bad.
Vast majority of Internet users are not security savvy. Doing a baseline scan with appropriate remediation guidance will go a long way.
I'm pretty sure security researchers will set up honeypots and monitor what the government probes are doing.