Then your choice is to move to another provider. It's that simple.
Well, it's not my choice, but Vobelics (I just jumped in the discussion with some clarifications). And as it is not (as established above) providers (Internet Service Provider is CARNet) fault, moving to another provider (ISP) is not going to help at all (as it seems you imply). Because, whichever ISP the the IRB chooses, their (IRBs) policy stays the same, and they would
still drop incoming ICMP echo request packets (as it is IRBs policy, and not of their ISP, which is CARNet).
Now the issue is
simple1 as you say, but not in a way you mention -- Vobelic could try:
- to talk to IRB network admins to remove that "ICMP Echo unwanted" policy or to request native IPv6 from CARNet (which provides it free of charge to all it's members). Pestering for native IPv6 is probably the best choice, if somewhat time consuming and of uncertain outcome -- but also of biggest reward.
- he could try to persuade HE.net staff to remove "ICMP Echo request" requirement if using "AUTO" script (which he did try and got refused)
- he could use some other IPv6 tunnel provider which does not require ICMP Echo, like sixxs.net AYIYA tunnels (probably the easiest way out)
- he could leave IRB (probably his place of employment I'd guess) for some other company
- he could give up on IPv6 for the time being
Ok, that last one is unacceptable, and
he might even argue that next-to-last is also somewhat extreme

Footnotes:
1 definition of
simple: "anything that one does not have to do himself/herself". Or, as we'd say in Croatian "lako je tuđim kurcem po koprivama mlatiti"