this is exactly what that means the server you are trying to connect to does not use the new ipv6 this is not the problem yes if you want to connect to an open public wifi then all you need to do is type in a terminal dhcpcd. or install wicd from slackware extra and let it be the workhorse it has been since 12.0
you have a profile set up to connect to your router at home hopefully it is encrypted.
so when you go to public wifi it is sending info not needed to connect (static conection or a passphrase) and being kicked out.
so configure the connection and (profile for it) as open and connect.
when the wifi or net card tries to auto dhcpcd it looks for IPV4 and IPV6 no IPV6 input then out put is
that tells you it has looked for it and it is not there.Thats ok 90 percent of routers are IPV4.
so lets say the router is the new IPV6 the out put would be configure net card for IPV6.
if you would have coneccted there would have been no out put. but trust me 99 percent of public wifi today is IPV4.