The thing is, delinking socialism from Stalin also means delinking it from the Soviet Union, disavowing everything that’s been done under the name of socialism as “Stalinist.” The “socialism” that results from this procedure is defined as grassroots, bottom-up, democratic, non-bureaucratic, nonviolent, non-hierarchical… in other words, perfect. So whenever real revolutionaries (say, for example, the Naxals in India) do things imperfectly they are cast out of “socialism” and labeled “Stalinists.” This is clearly an example of respectability politics run amok. Tankies believe that this failure of solidarity, along with the utopian ideas that the revolution can win without any kind of serious conflict or without party discipline, are more significant problems for the left than is “authoritarianism” (see Engels for more on this last point). [5] We believe that understanding the problems faced by Stalin and Mao helps us understand problems generic to socialism, that any successful socialism will have to face sooner or later. This is much more instructive and useful than just painting nicer and nicer pictures of socialism while the world gets worse and worse.

this is directly preceding it. Even if I accepted your frankly hilarious black book of communism death tolls, the argument here is that the soviet union and China still greatly improved the lives of the average citizen compared to what came before while facing huge problems that you would crumble upon immediately upon encountering, like imminent war from the west that they predicted and prepared for correctly. As far as your other claim, it's not nearly so simple as you make it out to be:

https://www.washingtonpost.com/news/worldviews/wp/2016/12/21/why-do-so-many-people-miss-the-soviet-union/ https://www.reuters.com/article/us-ebrd-transition-survey-idUSKBN1422U2/

edit: also, nia frome is a trans woman