Noting an author's biases/motives, like agarttha did, is useful. It's not the same as asserting that a conclusion is logically false because of the biases of the person who argued it.
In this case I thought it was rather obvious what the author's bias was and he doesnt't try to hide it.
It might be useful if they tried to conceal it. E.g tried to present themselves as an objective researcher at a think tank that takes money from general dynamics/lockheed or a journalist who clearly hastily rewrote a press release.
Broken clock shows the right time twice a day. Biased people being correct is an exception, not the rule. We should be suspicious of people with know biases.