Reuters is certainly not nearly "unbiased". It may be better than US partisan news sources in covering US events, but their biases show elsewhere. E.g. when a terrorist attack by vehicle happened in Israel, Reuters reported it as "Palestinian dies in ramming attack"[1]. The Palestinian who died was the terrorist, but Reuters found that unimportant to mention. Another instance is where Reuters invented a quote from Israel officials out of the blue [2]. There are more examples of this, I just took first two I had at hand. Reuters relies on local freelancers and local reporting bureaus, and some of them fall way short of their proclaimed standards.
Why not? It's like saying "surely, from the guys whose raison d'etre is to research nuclear physics, these accelerator data are not very convincing". These people find examples of media bias and publish them. How the fact that they are specializing in doing it somehow invalidates their results?
Your analogy is not quite correct. I'm not saying Reuters didnt slant those articles in those particular examples but it could be a honest mistake; this site will never report when Reuters slants towards Israel because that is against its raison d'etre, so your examples are unconvincing as to Reuter's purported bias.
[1] http://honestreporting.com/reuters-headline-palestinian-car-... [2] http://honestreporting.com/reuters-turns-rocket-fire-into-fi...