> This is not exactly free speech issue, because Twitter does not ban based on political preferences/opinions.

Freedom of speech encompasses far more than just "political preferences/opinions".

> This is dishonest competition (all other major companies do the same but not as blunt: Facebook, Google, Amazon for example).

1. I know of exactly zero other social media platforms that ban the mere mention of other social media platforms.

2. Precisely none of those companies are owned entirely by individuals claiming to be "free speech absolutists".

3. Mastodon is not a company, major or otherwise. It's a "competitor" to Twitter in the same sense that me raising chickens in my backyard makes me a "competitor" to Tyson or Foster Farms.