sorry to hear this happened. i would've been pissed too.
i hear about this sorta thing happening a lot, unfortunately... cops sometimes react too slow, and ppl get nailed for the driving/ riding behavior of someone else on the road simply due to mistaken identity... cops are ppl too, and they make mistakes. sometimes they write these kinda tickets just to save face after realizing they probably messed up..
i dunno if u can really make the squid pay for everyone's tickets. yes- he caused the problem. but, u guys did, after all, allow him to ride along with you when u very well could've pulled off the road or separated yourselves... and, even by ur own admission u were riding faster than the speed limit. it's really just a combination of bad luck...
try to fight the ticket by written declaration, if that's allowed in your state. or, go to court and fight it.