You’re right, there is not truly a “free speech right” on Imgflip, being a private site. It’s a well-known expression that has a habit of creeping in.
Better to say there are free speech “values” here. And they’re ranked pretty dang high on the list of things Imgflip values. But they are balanced out by a commitment to stop things like blatant harassment, violent content, porn (actual porn, i.e. nudity and sex acts), etc.
Racism, sexism, homophobia — those are also banned per site terms, but they’re also hotly-contested gray areas right now. Well-intentioned people disagree about whether content falls in that category, or what those things even are.
Yes, we do value free speech and debate on PoliticsTOO as well. But we draw the line in a different place than the mods of politics stream. And I personally believe it’s a misnomer to say “debate” can occur on a subject like Obama’s birthplace. The birth certificate was released. He was born in Hawaii, ergo was a natural-born U.S. citizen and eligible to be President. It’s public.
You either accept that reality or you don’t, and if you don’t, you fall deeper and deeper down a rabbit-hole in search of justifications for that belief. We will not platform such conspiracies.
If evidence later comes to light, like on the Wuhan Lab Covid origin story, that offers support to (or even proves) a thing that was once considered a conspiracy, then we’re subject to revising our stance. But not until there’s real evidence.