So, let me get this straight: founding a group 49 years ago means that "he's very clearly biased toward proving minimum wage increase's success".

This seems like a lack of familiarity with the scientific method. First, there's a hypothesis about the world. Then, that hypothesis is tested against evidence. The origins of a seasoned researcher's hypotheses about the world and their ideas of what they would like the world to be are not enough to impugn their ability to evaluate others' study design or the integrity of their own hypothesis-testing.

At best, you've provided evidence for "he may be ideologically more pleased with hypotheses supporting the success of minimum wage increases being successfully supported by evidence".