I think dogwhistle is a bit strong. They are being specific about democrats because the democratic party voting for this should have required absolutely 0 brain cells, and they are pointing out the possible reason for the cognitive dissonance.

Anyone paying half attention knows aipac is a problem with republicans as well, but we didn't expect them to vote to impeach hegseth because of tribalism alone, no need for further explanation.

The audience of the message was democratic voters, to reign in their party, not to the entire voting populace.