I think Twitter was well within their rights to refuse to allow their website to be a vector for what they considered to be foreign meddling in an American election -- something that they've been criticized for in the very recent past.
If it wasn't a foreign meddling attempt then it was a domestic one. To me this is less a question about Twitter's right to block stories (which it absolutely has) but rather a question of whether election meddling attempts should be recognized on their own as blockable or censorable content.
The most recent OTM had a segment about the way conservative groups have been following the Russian playbook, creating fake local news sites, taking advantage of underemployed journalists to seed real content as cover for disinformation articles etc.