Technically true, but you're missing the point and the heart of the debate. Yes they have legal standing to do this. Is it healthy for society though? A lot of people think not, hence why they're about to be bought and the board is likely to be replaced.
If you want to talk about free speech, talk about free speech. If you want to talk about the first amendment, talk about the first amendment. If you want to talk about something else - label and define it precisely.
It is critical to this debate that things be properly defined and labeled. As is patently visible in this discussion, people are trying to defend indefensible or unrealistic positions by shifting their meaning and playing with ambiguity.
Words have meaning, that meaning can be flexible to include common usage, but there is nothing inappropriate about calling out objectively problematic uses of words - especially those that are disruptive or distracting (c.f., Canadian truckers making 1st amendment claims in Canadian courts).
