Give someone an inch and they'll take a mile. It's not that it's just a mask, it's potentially a small step towards seizing our freedoms.
I agree that it does seem a bit irrational when just focusing on masks, but not necessarily when we take all of the response to COVID-19 that we've seen so far. The goalposts have consistently been moving, so I don't find it unreasonable that people want to rebel against more coercion.
I still hold to my principle that it is better to inform people of the facts and lead by example. Mandates will alienate people and force an underground/blackmarket of activities and ideas.