You can't reason with fascists so the 'but they say things I agree with sometimes' is irrelevant. Either you keep pushing them out of public spaces and undermine their ability to organise regardless of whether they manage to say something innocuous or dress nicely for once, or you're at best lacking in knowledge about how the movement functions but more likely a sympathiser.
Sanger has been voicing politically motivated antipathy towards Wikipedia for a quarter of a century or so, and worked for competing projects for most of that time. This includes supporting far-right nasties like The Heritage Foundation.
No, there are many other political movements I also disagree with, for example the broader reactionary tendency, including conservatives and neo-liberal groups.
Commonly I also disagree with people on ethical or religious grounds. For example I vehemently disagree with most protestants on the issue of capitalism which they consider compatible with the teachings of the biblical Jesus, and I while I agree with many catholics on this same issue I disagree with church mediated caritas as the social solution.
Frankly, I think you're the one that mostly comes across as scared here.
What am I scared of? I'm concerned for your grip on reality if you think a free market think tank is a bunch of fascists. That's about as factual as me calling Obama a communist.
Fascism is capitalism violently colonising its home turf, there is no conflict between a group calling itself a "free market think tank" and being part of a fascist movement or tendency.
Obama is quite pro-capitalism and hence much closer to fascism than any leftist position. As a politician he also invested heavily in and innovated deceitful application of violent force, mostly abroad, but kind of rolled out the carpet for it to turn explicitly fascist by 'boomeranging' back home.
I suspect insights like these frighten you, because they would force you to reevaluate your identities and place in society.
Not really. What other political tendencies perform violent colonisation at home?
And, well, yeah, they have a lot of similarities. They both agree on things like 'Arbeit macht Frei', extremely violent punishment of petty crime and industrial futurism regarding e.g. unrestrained extractive energy exploitation and so on. It's harder to figure out but it seems to me that the Manhattan Institute agrees with Hitler on the jewish question, jews need to be removed from 'white' societies, but disagrees with immediate industrial extermination and rather opts for the more palatable solution of having them migrate to and serve a colony. I.e. the kind of Madagascar plan that mainstream zionism amounts to, though it targets Palestine instead of the island.