I perceive the author to have been favorable to one side, therefore I discard all his evidence and argumentation.
Not discard, simply distrust. Remember all those Microsoft studies comparing the total cost of ownership of Windows and Linux? Finding flaws in the studies was hard. Discovering an a priori reason to distrust the studies was not.
Simply put, any article like this is going to make claims: "X is a fact." When the source is biased, and X confirms the bias, it's much harder to trust that X is true.
Bias itself is not a flaw in an argument. Bias may tell us where to look for flaws in the argument.