For the record, who is one of the Brietbart leftist advertisers?
If they are advertising there, doesn’t that by definition counter your claim?
On topic, he is espousing the battle Media Research Center has been waging for years and the MSM still is.
Breitbart is using ad managers, who aim their ads quite independently of what the sites are doing. Thus, here in Norway, I typically get political ads from Labour (deep red socialist) and affiliates.
And from socialist newspapers.