To me I can't really see how you can say that and then do a 180 and say that people are stereotyping them.
What exactly makes it hard to see how I can say that, or where is the 180 turn? They are mostly activists of one kind or another, and activists by definition are... active

. Most people are not as they don't want to challenge the status quo or are waiting for someone to take lead or think someone else will fix the problems (hence the bystander effect).
Trying to label anything in the group, if you can even call it that, is like trying to describe the shape of an amorphous blob. There is no boundary that says "you are or aren't a member", even, anyone can just claim "I am a member", nor is there any real level of cooperation among the people. Ultimately it boils down to a whole bunch of individuals doing individual actions, and in a few rare cases a small team of individuals doing an action; there is little unity besides the name.
Most of their actions are organized to a fair degree and most of the actions under anonymous are done by a large group of body. Spend a few minutes on their IRC channel and you'll realize how wrong you are in saying this. Yes, they are a loose coalition, but they are united in thought very often.
And again, I don't know if you can really call them a political activist group, either, simply because of the wide variety of things that have been attributed to the group. If you point to a whole bunch of charity work and say "X did it, and I'm a member of X so I would know", does it mean X is a group which focuses upon charity? If yes, I then point to a bunch of low-key thefts, and say the same for them. Is X still a group which focuses on charity?
Their actions (at least those that the IRC channel will own up to) all have a lot in common. Even those I disagree with (such as AntiSec) fit in with their overall train of thought (which is undoing and drawing attention to the things they see the government doing wrong, as demonstrated in their Walk on X support and their attacks on BART and other organizations). There are of course those that don't fit in, but the IRC channel will deny those being official operations (like Operation Facebook).