Are you an Internet sleuth?
That claim is attributing the action to a group. And the group in question is not well defined. You need to define precisely who the group or groups involved are and show evidence that it was an action of the group and not just individuals in the group.
I'll let the OP stand for his own claim, but when I write "internet sleuths posted photos clearly showing people they believed were suspicious", I mean nothing more or less than that individuals did so.
Moreover, it's clear that certain sites (such as Reddit, from what I hear) supported such speculation, insofar as they provided a particular subforum for these kinds of posts.
There is no group called "internet sleuths", so I'm not sure why you think that when we say "internet sleuths did such-and-such", we mean that this fictional entity collectively did it. But, in any case, that is surely cleared up by now: I am criticizing individual behavior, not group behavior.
ETA: Specifically, when I refer to "internet sleuths", I mean those
individuals who speculated online and publicly and in a non-professional capacity regarding the identity of the bombers. So, for instance, I don't have online professional journalists in mind, even though such persons may have also behaved very badly. The Post, in particular, behaved in a horribly irresponsible manner, but they aren't the sort of folk I mean when I speak of internet sleuths.
In fact, I assume that some Redditors active in the subforum were appropriately skeptical and argued that public, online speculation of suspects, complete with photos and sometimes names, is a bad thing. I'm not criticizing
those Redditors.