"Free speech means arguing against messages one disagrees with, or ignoring them, but not trying to suppress them."
Agreed, but "I won't provide a platform for this speech" is not "suppressing". If I put up a bulletin board in my front yard and encourage my neighbors to post things there, in general it's eminently reasonable for me to decide that certain things can't be posted - even if my bulletin board becomes the most popular one in town.
(But if it's made "the official town news source" and local government makes certain posting certain things illegal, that's an entirely different kettle of fish.)
Tangentially, there's a 4th option you don't mention for messages one disagrees with - censuring them. (As in "actively and visibly disapproving" - not "censoring"!) For some types of message, the most appropriate response is a firm, unmistakable "That isn't welcome here" / "That's a terrible thing to say" followed by no discussion whatsoever. (Eg: when arguing lends a platform / legitimacy, but ignoring implies acquiescence.)
Your fourth option is perfectly acceptable to me: exercising free speech right to say that original post is a terrible thing to say. However, we should not enforce the "no discussion whatsoever": if either the original speaker or another person wants to argue that it was not in fact a terrible thing to say, let them.
Agreed, but "I won't provide a platform for this speech" is not "suppressing". If I put up a bulletin board in my front yard and encourage my neighbors to post things there, in general it's eminently reasonable for me to decide that certain things can't be posted - even if my bulletin board becomes the most popular one in town.
(But if it's made "the official town news source" and local government makes certain posting certain things illegal, that's an entirely different kettle of fish.)
Tangentially, there's a 4th option you don't mention for messages one disagrees with - censuring them. (As in "actively and visibly disapproving" - not "censoring"!) For some types of message, the most appropriate response is a firm, unmistakable "That isn't welcome here" / "That's a terrible thing to say" followed by no discussion whatsoever. (Eg: when arguing lends a platform / legitimacy, but ignoring implies acquiescence.)