Anti-maskers weren't being condemned for pointing out that ersatz cloth masks weren't very effective. They were condemned for levying that criticism as if it was a justification for doing nothing, as opposed to an argument for more effective off-the-shelf respiratory protection.
(I ignored your attempt to drag "mandates" into this, because the primary aspect is personal behavior. I've yet to see an anti-mask-mandate protest/movement where everybody voluntarily wears respirators and distances, while philosophically arguing against legal mandates for doing so. And I would remember if I had, as this would align with my own politics)
But none of the mask mandates--at least in the USA--have required masks that significantly work. So you have a law that requires uncomfortable masks that make it hard to communicate, but don't significantly reduce transmission. "Well some masks do work!" is not a good counter-argument, especially when its clear that nobody really expects the public to be able to wear the good mask the correct way.
You are asking them to respond to an argument the pro-mask contingent was afraid to even make.
Yes, the mandates as they currently stand are lame. But the anti-maskers are using that senselessness to argue for rejecting the whole idea of wearing any respiratory projection, which they demonstrate by personally choosing to not wear respirators. As I said, their argument is not akin to "respirators protect against the spread of Covid but the government shouldn't be mandating specific personal behavior", but is rather rejection of the whole subject.
For an illustration of the difference, I recently had some trouble entering a hospital due to their mask mandate - they seriously insisted that I take off my P100 respirator and wear just their cosplay mask instead. I was able to escalate to someone higher up and find a (more but still not entirely sensible) compromise that they'd let me wear my own N95 under a cosplay mask. Where is the political group that represents my predicament, which was caused by a broken centralized mandate? It's certainly not in the unmasked people berating customer service people for enforcing some basic pandemic etiquette!
> nobody really expects the public to be able to wear the good mask the correct way.
IMO this was a terrible groupthink counterargument (aka straw man) led by the other political team of ersatz maskplayers and condescending healthcare workers, following from the early central authority lie that respirators are ineffective (in order to reduce consumer demand for them). The red herring that wearing a mask primarily protects others also followed from this rationalization of ersatz cloth masks.
The open society / freedom approach is that you treat people like adults, assume they can understand a mildly complex thing, and then increase education to help everyone do better. Instead two years later we've still got the two political teams arguing over which stupid approach is better, while mostly looking at anyone who wears more effective respiratory projection as some aberration.
If I had been in charge of pandemic response, I would have sent everybody a kit including a N95 mask as soon as possible, and made it clear that the primary reason to wear a respirator is to protect yourself and your family. Then I would have ramped up production of elastomeric half face masks (which are more comfortable and thus more sustainable), and perhaps just given those out as well - their (pre-pandemic) cost of $30 per person is peanuts compared to what we've lost. These utterly backwards post-reality memes spread by both political teams have caused so much needless death and suffering.
(I ignored your attempt to drag "mandates" into this, because the primary aspect is personal behavior. I've yet to see an anti-mask-mandate protest/movement where everybody voluntarily wears respirators and distances, while philosophically arguing against legal mandates for doing so. And I would remember if I had, as this would align with my own politics)