Given those facts, that would be a reason to consider Miller to be leftscum. The fact that they also use an ad agency that has leftist clients might be considered as supporting circumstantial evidence, but of VERY little weight!
Counter-example: If I get a ticket, I’m going to get a lawyer who probably has defended rapists, murderers, and other thugs. Does that make me a supporter of rapists, murderers, and thugs? Of course not, it makes me someone who needs a lawyer and whose money is green!