This is a fair statement of the issue, though it must be posed again for each separate occasion that a black bloc appears. Judgment of one appearance does not carry over to other occasions, since the "membership" of black blocs is so apparently fluid.
I do prefer not to multiply technical terms beyond necessity, and I do not see the need for either "elitism" or "adventurism" in this thread.
It would be useful, however, to use "non-violent" in its original technical sense and not use it interchangeably with "peaceful." "Non-violent" in fact is shorthand for "Non-violent civil disobedience." It is deceptive when used merely as a synonym for peaceful. Also, as several have pointed out, Violence (on the whole a meaningless term since it covers so many radically different actions) should at least be confined to action which physically harms other people.
Carrol