If you don’t have the freedom to cover your face at a political protest, the country you are protesting in is not free.
If you don’t show your face in a political protest in a free country
OP sure did.
Why is it cowardly? What do you think the purpose of a protest is? Your face does not lend a protest additional credibility, it just makes it easier to target you. The purpose of a protest is to show that people support a cause. Who those people are is irrelevant unless you plan to target them.
It is cowardly to hide behind a mask in a free country where you have nothing to fear of government from protesting.
I do however agree that it is sensible to mask in a country where protesting in and of itself will arrest and mistreatment from the government.