It did not need to be so.
I have been a Wikimedian for 20 years. I have seen loads of nasty debates, including political activists (e.g. anti-nuclear, antisemitic Left, specific interests such as the Bogdanov Brothers...). We essentially resisted these attempts.
I also remember individual fascists at the beginning: they kept having tantrums, leaving and rejoining the project several times in a row. They were abhorrent, but inefficient.
But this has changed.