You have to be willing to entertain evidence from biased sources when you’re considering politically charged questions. By all means, consult evidence from various ideologies, but don’t hold out for unbiased scholarship that will never exist.
“Does welfare make people less productive” is not a political question. We can measure welfare and we can measure many aspects of productivity and activity. We can make a quantitative answer to that question. Opinion and ideology is not evidence.
Saying that we need to consider opinions on the same level as actual observations because “political” is fundamentally wrong.
What is political, and must be, is how we act on those findings, the answer to the question “considering those facts, what do we do?” There are many possibilities that are worth discussion, from doing away with welfare entirely to UBI. But this must be based on facts, not ideology. Think tank opinion pieces belong here, in the political discussion.