Argument by adjective is a fine enough fallacy. You have an argument whose sole strength is an adjective rather than fact or the logical necessity that only one case is possible. However, a more general idea is argument by descriptor.
For instance, there is such a thing as argument by metaphor. To take an example, if someone says that since rocks and the weather are mechanistic and you don't debate with those (which is incorrect; damned thunderstorms *shakes fist*), you shouldn't debate with a mechanistic human. This is obviously flawed because it is taking a metaphor, stretching it beyond the breaking point, and saying that the ends should therefore be heated up due to the recent break.
It reminds me of the ads from the RIAA people were parodying on here. "You wouldn't download a fish..." was probably the funniest. In a similar way, "You wouldn't drive a rock, therefore you shouldn't drive a car" implicitly defeats the earlier argument by metaphor. Even the person proposing the argument differently manipulated different things even he considered mechanistic.
This can be seen even more directly because it contradicts the conclusion of a valid argument with the same premises, and so it cannot itself be valid. If determinists act according to programming, and they're programmed to debate, then to be consistent with determinism...they'd have to debate.
To take a simile that's valid on some basis (humans are like rocks because they're mechanistic) and to propose that other bases for the simile (humans are like rocks because you should interact with them in the same way) must consequently be valid is a completely invalid argument.
To be clear, I'm not a determinist.