Sincere answer, in pieces:
1) We already proved he cheated. Whether others accept the proof or not is beyond our control. A reasonable RD and race committee would have DQed him post haste.
2) Some ideas that seem grandiose have already been actualized, like creating a video of five check points that tracks every runner and shows the odds of him running and not being photographed are one in 572,000. Can you imagine the work that went into the grandiose idea?
3) Whether to follow through on a grand plan to reach out to the runners and try to rally them, or to start a social media campaign to boycott the race altogether (#boycottlehigh) is doable but begs the question: Do we want to attack the race itself because a few people are cowards or morons? Do we do a disservice to the sport through such an action?
(By the way, I know that a "huge" boycott would not happen. However, I do believe we could dent the participation to the tune of 10 to 15%, which is painful to the budget of such an event. And a boycott could be supported by a call to donate directly to the charity, which could yield them more money in total and would help avoid the accusation that we are hurting a charity.)
4) Mike has already lost. Sure, he got to run Boston and he hasn't been DQed (yet, if ever). But ask yourselves, if these articles were about you, have you won?
http://www.runnersworld.com/general-interest/via-marathon-no-evidence-marathon-dad-cheated
http://www.phillymag.com/news/2015/06/01/mike-rossi-boston-marathon-dad/
http://www.runnersworld.com/newswire/questions-arise-over-how-a-pennsylvania-dad-qualified-for-boston
http://gearjunkie.com/mike-rossi-marathon-cheater-boston-marathon
http://sports.yahoo.com/news/-dad-of-the-year--boston-marathon-runner-under-investigation-over-qualification-questions-205004421.html
If these videos, showing a guy isn't in a race, were about you, have you won?
https://www.youtube.com/watch?v=DxKfEiOfGmY
https://www.youtube.com/watch?v=vGilRGr2GlI
If the best claim you have to innocence is this tepid press release, which basically says, "he may have cheated but the evidence isn't conclusive but we'll do better next year," have you won?
http://www.kintera.org/htmlcontent.asp?cid=666508
No, if Mike Rossi ever cared about running and being a part of a running community or sharing in the mutual respect that runners have for one another, he knows that he has lost spectacularly.
So that's where we stand today, as I see it.