Obama Fan Base is both accurate (historically and sociologically), and isn't dehumanizing. (VL probably should have taken me to task on the the Boing Boing post, but I couldn't resist....)

standing for the actor. It is, among several types of figures of speech, a form of metaphor.

Using "Obot" actually is no more dehumanizing than calling an assassin a "cutthroat." The action of the person may not be laudatory, but it is something the person does. Conversely, to call someone a "saint" is not to say the person is dead and has been canonized; it indicates that actions by that person are considered good, saintly. In this case the actions are considered laudatory; since good actions can be saintly the person may be called "a saint." It's simply a shorthand way to say something about that person. Figure of speech.

If a person tends to have a reflex action about something, in this case praise or defensiveness about Obama, "Obot" can be a representation of that aspect of the person. It does not dehumanize, ableit its current connotation, at least among some people, is negative. The connotation is perhaps what has lead to the current troubles with the use of "Obot."

On further thought, however, perhaps "Obot" is a metonymy (from Wiki):

Metonymy...is a figure of speech used in rhetoric in which a thing or concept is not called by its own name, but by the name of something intimately associated with that thing or concept.
SNIP
Metonymy may be instructively contrasted with metaphor. Both figures involve the substitution of one term for another. In metaphor, this substitution is based on similarity, while in metonymy, the substitution is based on contiguity.

Metaphor example: That man is a pig (using pig instead of unhygienic person. An unhygienic person is like a pig, but there is no contiguity between the two).

Metonymy example: The White House supports the bill (using The White House instead of the President. The President is not like The White House, but there is contiguity between them).

In cognitive linguistics, metonymy refers to the use of a single characteristic to identify a more complex entity and is one of the basic characteristics of cognition. It is common for people to take one well-understood or easy-to-perceive aspect of something and use that aspect to stand either for the thing as a whole or for some other aspect or part of it.

Metonymy is attested in cognitive processes underlying language (e.g. the infant's association of the nipple with milk). Objects that appear strongly in a single context emerge as cognitive labels for the whole concept, thus fueling linguistic labels such as "sweat" to refer to hard work that might produce it.

The Wiki entry compares metonymy with synecdoche:

Synecdoche, where a specific part of something is used to refer to the whole, is usually understood as a specific kind of metonymy. Sometimes, however, people make an absolute distinction between a metonym and a synecdoche, treating metonymy as different from rather than inclusive of synecdoche. There is a similar problem with the usage of simile and metaphor.

When the distinction is made, it is the following: when A is used to refer to B, it is a synecdoche if A is a component of B and a metonym if A is commonly associated with B but not actually part of its whole.

Thus, "The White House said" would be a metonym for the president and his staff, because the White House (A) is not part of the president or his staff (B) but is closely associated with them. On the other hand, "20,000 hungry mouths to feed" is a synecdoche because mouths (A) are a part of the people (B) actually referred to.

An example of a single sentence that displays synecdoche, metaphor and metonymy would be: "Fifty keels ploughed the deep", where "keels" is the synecdoche as it names the whole (the ship) after a particular part (of the ship); "ploughed" is the metaphor as it substitutes the concept of ploughing a field for moving through the ocean; and "the deep" is the metonym, as "depth" is an attribute associated with the ocean.

Is it a metaphor? Yes. A synechoche? Now I'm not sure; strong possibility.. A metonymy? Most likely. Certainly, is a puzzlement!

An Obama supporter praises and defends Obama no matter what; it's like he's a robot programmed to do so. Hence, "Obot." Or "bleeding liberal hearts" always support single payer; it's like a reflex action for them. Hence, "kneejerk liberal."

Any linguists, PhD's in pertinent studies want to tackle this?

Anyway, perhaps "Obot" should be banned or used carefully simply because it has considerable negative connotation.

But...where does that approach stop?

I say synecdoche, you say metonymy--I'm calling the whole thing off...and going out into warm sunshine. Transplant some daiseis and black eyed susans coming up where they oughtn't be growing.