If you're going to complain about the Koch brothers or other republican billionaires donating to their politicians or causes, and say that's a bad thing, it is at least reasonable to expect a fair person to be consistent and similarly list Tom Steyer, Michael Bloomberg and George Soros among the people corrupting the systems.
Well, I do. I guess I have your blessing. ;)
If you complain about corporation, the exact same complaints need to be levied against unions.
I disagree here because unions don't have shareholders that expect higher profits each year nor share in those profits. While corporate leaders will claim they speak for all their employees and are, of course, only working in the best interest of said employees, it's hard to believe when they donate to politicians whose platform is dismantling worker and environmental safety protections and pitting domestic and foreign workers against each other in a race to the bottom.
While there are certainly stories of union bosses taking advantage (lavish parties, travel, etc), that happens in corporations as well and boils down to human nature. I'd bet that not every member supports every deal union bosses make, at least the members can elect new bosses. What can workers do when their employer donates to a candidate they don't support? Nothing. And where does that donated money come from? From the products and services the workers make/perform.
"Thank you for your tireless effort making widgets at ACME. As we don't like having to pay disability when our machines chop off your limbs, we've decided to take some of the revenue we earned selling the widgets you built and donating it to a candidate who will work tirelessly to dismantle disability insurance. Game on!"
That being said, I would prefer all campaign contributions be small and individual. There's no reason unions and corporations can't explain why they believe a particular candidate is good for their members/workers and leave it at that. I may feel the "nefarious factor" of union versus corporate donations differ, I'm not in favor of exceptions for certain groups that allow them to donate unlimited, anonymous funds to candidates or issues.