Misleading headline. The protesters were not really defying the lockdown since the constitutional right to protest has not, at any point, been suspended. It is kind of like saying people are "defying the lockdown" to go shopping.
Good on them I say. This government especially needs to be reminded that people power exists to balance that of their own no matter how much it wants to see everyone locked up in their homes while they try to push through various self-serving laws and reforms with urgency that are not even related to the crisis to give the illusion that what they are doing is somehow supported by the masses.
As for the health critiques, sure these people put themselves at risk. Personal responsibility comes in to play as much as it does when you are out shopping or going to the park during the weekend. A protest is however unlikely to make a significant dent in the numbers that had already taken off into the stratosphere during times of strict lockdown anyway.