Earlier quoted context omitted.
This might be reading too much in to minor drama at a diabetes conference. The gentleman in question could have gone to protest outside (and probably did). The article linked doesn't even say what exactly they were protesting (beyond a rather vague "attacks on scientific research" which could mean a lot of things).
Their so-called "protest" was just distributing an article already published in the journal of the medical association to which this conference is attached, which probably discussed matters of interest for the attendance, like the future of research financing in this domain. I can hardly think of a more peaceful form of protest, which only intended to make aware the participants about the content of the article. Thos…
The first amendment applies to public spaces. Not private conferences which are invite-only. You're on an anti-U.S. tear in this discussion but lack understanding of the basics.
For the same reason I can't show up at your office and start handing out religious materials and/or pornography (take your pick) to everyone showing up for work and claim it's a free speech issue and my right to do so.
As someone else pointed out below, this exact argument was used to ban apps lacking "correct" moderation from the app stores a few years ago.