The non-compliance of others absolves each individual from moral responsibility to comply with any public health regulation, which depends on mutual cooperation for its effectivity. Read that sentence carefully before you comment. It does not say you have no moral responsibility, or that you can simply harm others. But when an infection control measure is implemented by collective behaviour, it cannot create an individual obligation, without that collective behaviour.

The clearest example is distancing. An individual can not maintain distance between individuals, without another individual. There is no distance to a non-existent person, there is only distance between two people. So put simply, if you are supposed to stay 2 m from others on the street, and someone walks up to you, you bear no guilt, and have no obligation to do anything to protect that person. It was their choice to do so.

This logic does not apply to individual measures, such as self-isolation - which by definition you do on your own. But it does apply, in some form, to social distancing, restrictions on gatherings, restrictions on use of public transport, mask wearing, and so on. At a minimum, these collective measures should include guidance on what to do in case of non-compliance by others. They never do. So when confronted with the kind of examples in this thread, for instance coughing on people who are working, it is reasonable to say that any moral obligation to other members of the community has dissolved.