The links your citing rely on obfuscating numbers and cherry picking the types of spending they're focusing on. It's almost like that's an intentional aspect of campaign financing...

The WSJ article you link straight up admits they're looking at a study that cherry picked some groups to compare:

However, what about the fact that 11 of the top 20 political-donors are labor-unions?

The entire premise of this devil's advocate retort is false.

That "Open Secrets" article you sent pretty much refutes the idea that business spends more than labor. See the "caveat" in that article. It is clear that labor unions donate way more than business.

Not really. Your friend didn't read the last sentence I guess:

Still, the base of large individual donors is predominantly made up of business executives and professionals."

Labor-unions far out-donate businesses, and the Dems far out-fundraise the GOP in many cases b/c the Dems live in the wealthy areas.

From there your friend is just falsely asserting labor unions outspend everyone else. But of course wealthy people donate to Democrats. Who said they don't? The real chilling effect of political money is it drives out people hostile to the interests of capital. This is still true even if it were the case that liberals out spend conservatives.