Example:
"takes a disproportionate amount of effort to refute" -> This is a pretty decent definition of toxicity -> Silencing it is really the only effective way to deal with it.
Edit: I'm not asserting that this particular case is in fact toxic. Anyway, it's subjective.
In the abstract, something is toxic if it disrupts or makes impossible desired processes even in very small amounts. Trolling is obvious, conspiracy theories are closer. Some things inherently generate more heat than light, suck oxygen out of productive conversation. You don't have to be a radical leftist (I'm really not at all), you can just watch it happen here or any other forum.
The ProPublica article calls out Warren Buffett for tax avoidance, even though he simply had less income. I question the integrity of the writers who want to slander Buffett, who has been extremely outspoken about increasing the taxes rich people pay. There exists no tax on unrealized gains, and Buffett did not realize gains, so why would they try to make an example out of him by falsely accusing him of hypocrisy?
How do you claim someone is avoiding a tax that does not even exist?
While they might have a point about needing to tax unrealized gains, they certainly went about it in an inappropriate manner, more suited for a tabloid rather than a respectable outlet for journalism.