The 'default' resets during a pandemic, especially when transmission is high. Your exhalations are a highly likely cause of harm
Even at the peak of the pandemic, only a small minority had the virus. So no, it's not true that "your exhalations are a highly likely cause of harm." Statistically, it's highly unlikely in fact.
In both cases, the single encounter with exhalations may or may not cause direct harm. But for both, the cumulative effect of any escalations poses a real risk.
Not really. Inhaling cigarette smoke is always bad. If done only rarely, it's unlikely to do you much harm, but it's easy to identify a person who chooses to smoke and quite reasonable to ask them to take steps to protect others.
With face masks, the vast majority of people's 'exhalations' will not be harmful, though it's hard to know which. During the peak of the pandemic, it's reasonable to ask for universal mask wearing, but as vaccination rates increase and the risk to the general population falls, there comes a point where it's reasonable to say they are no longer a legal requirement. It's debatable whether that point will be reached on July 19th, but sooner or later it has to happen.