I fear you can have a response for the second part of your question only by reasearching and taking a position by yourself. Losurdo questions the western traditional view on "totalitarism" and he wants to distinguish "stalinism" and "maoism" from "nazifascism". He does this introducing the concept of "despecificazione" (the esclusion from civil community of an individual or a group) which according to him can have two natures: one based on political idea/morality, the other based on biology; the first, linked to stalinism, can be changed unlike the second, which is Linked to nazism. He does not condone stalin for his criminal methodology (he states if i recollect correctly that it was even more criminal being stalin a "socialist" leader). But he notices and writes about the ipocrisy of the liberalism (above all the exercise of it, which has reached levels of inhumanity comparable to and maybe even greater than totalitarian regimes did). Being the western modern society based (partly or not) on liberalism he thinks that a critical approach on the "totalitarism" that would not take account for the differences like despecificazione (and others) is at least biased or silly if not politically oriented against communism or pro liberalism. Political ideas are personal and even if historians have the duty (or hope? :) ) of objectivity they are persons: everyone is biased and prejudicial of or towards something; to me the match-point is to verify if my interlocutor is conscious of his bias or not, and if they are willing to adapt to different and multiple points of view.

No, that assertion is pretty groundless. Plenty of important Soviet scholars are/were socialists or use class-based analysis (E.H. Carr, R.W. Davies, Donald Filtzer, Moshe Lewis, Lewis Siegelbaum, to name a few). Funnily enough, these scholars generally have negative integrationists perspectives on the Soviet working class - that is, that the state coerced the working class to go along with its policies - whereas the very anti-communist and liberal Stephen Kotkin actually has a positive integrationist view - that workers and the state generally had interests which aligned, especially as the state gave the working class particular privileges/social status.(1) Even the totalitarian school, which gets ragged on quite a bit for being a bunch of biased Cold Warriors, has had a revival in the past decade by historians like Amir Weiner and Mark Edele who base their works on detailed archival research.

(1) - See Kenneth Straus, Factory and Community in Stalin’s Russia: The Making of an Industrial Working Class, for a more detailed summary of these perspectives