It's not about conflating freedom of speech and having a platform. It's about discrimination by businesses. We have laws in place preventing businesses from discriminating. A shop cannot say "we don't allow black people here" and hide under the excuse of "oh but there's plenty of other shops you can go to". A platform should not be able to saw "we don't allow X people here" and hide under the excuse of "oh but there's plenty of other platforms you can go to".