Discussion of the involvement of the Bielski group with other partisan groups in reallife belong on the article with the group. Wikipedia has an obligation to document the controversy, including of course the statements of supporters of the group as prominently as critics of it. The question here is that it is usual to discuss in  historical film the question of how true to history it is. Considering that the very involvement is uncertain, the wording here would have to be very tentative. Whatever is here or anywhere has to be in neutral non-loaded language, as elsewhere in Wikipedia. Anyone who actually doesn't know the reputation of the NKVD can find out from the article on them, we do not need to use the word "feared". The way to deal with topics as difficult as this is as soberly as possible. For one thing, it gives less of an impression of propaganda. In other words, Gwen is completely right in her sentence at the start of this section. '  
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