You can be broadly for cities rolling out their own broadbands while still pointing out that on the long term your local government growing its spending can be an issue.

10Gbps is absolutely great, but then the city might create an entire bureaucratic structure around it and in 30 years when it's not great anymore the apparatus won't die or be displaced like a company eventually would.

Which is not to say that in this scenario this is not a bit of a farfetched scenario considering that's precisely what the incumbents are doing as you pointed out.