Maybe this explains why they did not want to lose out on pieces from multiple other contributors. Include you, and run a piece that appeals to some fraction of 50 readers at the cost of losing out on the opportunity to feature other contributors, or exclude you, and run multiple pieces whose expectation for readership is higher. Theoretical arguments based on the supposed value of principled liberalism are not worth very much to people whose concerns may include things such as basic living expenses, and not alienating large numbers of academics, so they might be able find a job someday.
Frankly, I don’t see what all the fuss is about. If you want the authority to decide who gets included, and why, be an editor, not just a contributor.