That way lies madness. Senders have no such rights, and the determination of a message's legitimacy lies with recipients (and perhaps infrastructure owners) NOT senders.
How is the recipient of a message that has been blocked before he sees it to decide whether it was legitimate?
Why would you care, unless you are the receiver? If I decide that all ICMP traffic from IP addresses that have an odd number of "1" bits in it is not legitimate and shall not be allowed to reach my web server, then that seems to be a matter between me and my psychotherapist. I'm not sure why it would matter to anyone else, including rebuffed senders or NANOG's philosophers. What this all begs for is a reference standard for "presumed legitimacy" so that senders can know without waiting for complaints nor seeking explicit permission, just what kind of traffic they ought or ought not send. As I said in another note here, such a standard would have to be written in terms of assertions rather than negations. A peering or transit agreement is quite explicit since the parties and their specific concerns are known: it can therefore be of the form "All is permitted except X, Y, and Z." Presumptive traffic legitimacy or "implicit welcome" is between unspecified parties who can by definition have no specific concerns and so the standard must take the form "All is prohibited, except A, B, and C."