I don't know which view it is you're talking about, but what @dang did isn't universally wrong. If the view is something that is as close as possible to objectively wrong, in the moral sense, as something could be, I'd say it's justified.
An example of this could be genuinely stating "Hitler did nothing wrong" or "black people deserve slavery". You know, reprehensible stuff. There's no reasonable way to have that discussion. How do you debate whether a large minority is inherently sub-human? Like, I'm sure a Neo-Nazi would be able to calmly explain their views without attacking me (a white man) personally, verbally, or physically. But their view is inherently an attack on the humanity of other people.
To be clear, I'm not saying you are actually a Neo-Nazi or a racist. They're just very, very clear-cut examples of the point I'm trying to make. Another example could be that someone stating that every LISP programmer is a child molester. There's no flamewar in the comment itself, but it's a view that can't be expressed without inciting one.
Yet another example could be thinking that every person earning more than $50k is a capitalist pig and deserve the guillotine. Again, calmly stated as a matter of fact. But it's also calling for the execution of a large part of this site's audience. It would inherently cause a flamewar too.
All of these examples are extreme, but I think the point that some views inherently having a piggybacking flamewar has been made. Where @dang decides to draw the line between controversial point with legitimate room for discussion, and views so abhorrent or nonsensical that it's easier to simply ban users perpetuating them is up to their discretion.
I also don't think @dang bans people because of a single comment, but rather someone continually pushing the view that inherently leads to flamewars.