The existence of news articles that convey a negative impression of a person or organization, regardless of quantity, does not, in and of itself, indicate any bias, either in selection or presentation.
> There is an ongoing coup in Venezuela, with illegal arrests but somehow the very same Russian - Trump news remains more important.
The Washington Post and New York Times are US newspapers. The President of the US, and his close associates, involvement with Russian government is more important news for them than the auto-coup in Venezuela for the same reason that that auto-coup is more important in Venezuela than the Russia-Trump issue.
It's a much more insidious bias too because its harder to point out. You will have to use non-mainstream sources as they are the only ones doing the covering, and the fact that they are not mainstream will be used to hand waive away the complaints.