Same, and you absolutely should do that, just not as part of the "official" group. The organizers say that because one of their primary concerns is not escalating things, since a lot of people who might be part of the "official" action are probably pretty vulnerable, and generally it's a priority to keep them safe. Having a separate group of people (ideally in black block) ready to throw down is also a good tactic (at least sometimes), but they're separate from the "respectable" protest group for a reason.
This can also go south so be mindful of the situation. Certain escalations can get those vulnerable people arrested even if the black bloc group is distinct.
A good tactic is to split the group as a diversion, separating the vulnerable from the rest (while not making it obvious - half the black bloc should stay with the vulnerable), and allowing one of the splits to go do cool things. This way, the vulnerable will be blocks or miles away when things go down and won't even see it happen but the cool things can still go down.
Depending on what the protest is about, the counter protestor is likely just going to be shouting or attempting to drown you out with noise. Doesn’t warrant anything but a snicker.
But if you must, do it afterwards. Follow them to their car and beat their ass if you think they don’t have a gun or mace