Since when has it been the primary function of discussions to change anybody's mind or to persuade others?

There is at least one person here who regards anyone who holds opinions different to theirs to be pointless debating with, and only worth abusing.

Yes, forums and discussions are partly for airing opinions; but one would also hope that, if there are contentious issues, one's arguments would encourage others to rethink there opinions.  Isn't that what debates are partly for?