I have seen this kind of thing before, where a hacker gets into your account, doesn't change anything but then goes on to post malware or scam threads without your knowledge. You only get a wake up call when you are tagged.

It's so hard to prove that you were not the one who posted that stuff. However, the members who tagged you are understanding individuals and if you explain to them calmly and very well, they can remove the tags.

Another option, if you are really desperate about clearing your name and don't mind much about privacy is PM them your  IP logs from https://bitcointalk.org/myips.php. If you are concerned about your privacy, You can blur IP address and City and then provide them with only time and the country the IP address that made the post was from in comparison with your previous or current IP addresses(This helps if you haven't been using different VPN locations)