Uncharacteristic Assumptions

In the reading of A History of Western Philosophy over the weekend, I noticed a passage seeming out of place in Russell’s writing. He says:

Considered purely as a philosopher, Marx has grave shortcomings. He is too practical, too much wrapped up in the problems of his time. His purview is confined to this planet, and, within this planet, to Man. Since Copernicus, it has been evident that Man has not the cosmic importance which he formerly arrogated to himself. No man who has failed to assimilate this fact has a right to call his philosophy scientific (emphasis added).

This assertion on Russell’s part seems to me not unlike the kind of statement which he might sarcastically ridicule in the writings of another. The unqualified statements alone are against his merit in regard to this brief passage. Granted, Marx very well could have been too much a product of his time and its issues, but to criticize him for being so confined to the issues of mankind seems overkill for Russell, who often strikes me as a fair author. What is worse to me, however, is his accusation against any thinker who may not come to similar conclusions as Russell in observance to Earth’s place in the solar system. Who is anyone to insist we hold a place of comparative insignificance in the universe based on our orbit of a star? Compared to what? How may one infer that a planet not being the physical center of the universe is any reflection on the cosmic significance of the planet’s inhabitants? It strikes me as contradictorily arrogant to state that “no man” may have his philosophy taken seriously if he does not follow what Russell deems (but not I) an obvious and safe assumption. Russell could be right, or he could be wrong; either way, philosophy is all about the identification and breakage of blind assumptions. It seems to me Russell uncharacteristically failed in this task in the above passage.