I think that very few of these arguments are being made in good faith. For some people, any bias monitor is a barrier to sharing propaganda as news. Others just don't understand how to use the site properly. Or use it in a really stupid way anyway. Like this:

1. Look at the ratings.
2. If something strikes you as odd, run around screaming like your hair's on fire.

Instead of:

1. Look at the ratings.
2. If something strikes you as odd, read the part of the report that explains the rating.
3. Decide how important those things are to you and whether it's a deal-breaker.

Others are like, 'it's telling me what to think, man!' who don't seem to understand that those pages contain a wealth of information that you can include in your decision-making (or not). They've convinced themselves that it's presented as the one and only source of absolute truth, which is really just something they made up to be angry about. No one but them is making that claim.

There also isn't another free source that has that info in one place. There's no better place to quickly find news org ownership info, the country they're operating in (with links to info about press freedom in that country), and their history of factual reporting. But those people don't care -- they're just viscerally reacting to the ratings, not reading the reports.

I generally think their overton window skews right and every once in a while I've seen some huge fumbles, but overall they're more pro establishment than anything else. The only thing I've ever seen that could even be seen as pushing misinformation is their bellingcat rating, where they gave them "mostly factual" because they lost a lawsuit IN RUSSIA about how they were making "libelous claims" about the MH17 shootdown and who was responsible because their quite rigorous research showed that the Russian government was lying. inb4 some .ml tankie comes to go "uhm actually bellingcat is cia