Whether it is a Hillul ha-Shem or a Kiddush ha-Shem is a political question. If you are “blue” you probably believe that the measures to stop Covid19 are matters of pikuach nefesh, and the government is acting reasonably to fulfill their duties under the public health laws. If you are “red” you probably feel that Covid19 is not a serious public health threat, except for people who due to age or infirmity should probably not be going out in public to begin with, and the the actions of people such as the New York City mayor are the acts of a bigoted tyrant using the pretext of public health to crack down on he considers to be his enemies. If you are “red”, then davening in shul without a mask is a courageous act of civil disobedience against an unjust government, and as such is a kiddush-ha-Shem (though like many acts of civil disobedience, perhaps a bit foolhardy).
In a city such as Baltimore, where the local Vaad ha-Rabbanim is issuing restrictions going far beyond those of the government (and observed by most but not all shuls), it could be argued that following regulations issued by the local Vaad (which is “our” government) is mandated by halacha even if those issuing the regulations are misguided and poorly advised in their secular knowledge (though no one would accuse them of having an ulterior motive).
One should note that in many circles, proper dress includes useless items such as a necktie, so it seems can go along with adding a useless mask, especially if it matches the useless necktie. One should note that while the utility of a mask to prevent Covid19 is debateable, there are reports from the southern hemisphere (whose winters occur during our summers) that mask wearing reduces flu and colds, and there is a possibility that masks will become part of standard fashion.