Third, yes it's his opinion, but he makes some very good points. I'm not even sure what you mean by "bias."
His points are by no means more credible than those of any other Godfather fan. He basically presumes that Fredo would have done everything himself, including killing those assassins, and uses this as an argument to support his case. However, he somehow overlooks that Fredo had his own men, and that it is common practise that he would have used those men to do the "dirty work" for him. If he wanted to write an objective, and unbiased article he should have considered every possibility. The reason that he declines to do this shows that he was prejudiced from the start.
He did not have
zero motive, like I've states before, he would have always been second choice as long as Michael was around.