I don't think the diodes in that relay box should befome damaged, as they are directly protected by the 30 a main fuse, behind the batt, at the main relay...
If any diodes took a hit at all, they would be the ones in the regulator/rectifier, the metal case that sits up uñder the bike, in front of the rear tire...and that box is ealed and non servicable... might try a plug and play from someone you know, or trouble sshoot it as Directed in the FSM
The 30 amp fuse will not protect against reverse polarity - the diodes will fry because the positive voltage went the wrong direction, could take way less that 30 amps to fry those diodes.
I'm not willing to start an argument, so you may be correct... but unless you have consulted the wiring diagram on the bike as I have been doing currently,
I will verify my statements further, by adding this;
The o/p found his error in wiring prior to attempting to start the bike, and corrected the wiring.
Unless the "run" switch was on, and the kipass stoveknob switch was activated, and followed by hitting the starter button, the diodes in the relay box were not actively "working / seeing current" in the circuits at the time, and would not have seen the spike.
This bike has a very robust electrical system, with numerous protection stages, which have been documented over the last 10 years by peoples reports of mis wiring things, having acid leaks that destroyed the main fuse and relay, creating meltdowns in wires, and various others "oops" scenarios..
I'm personally hedging on something fairly simple, and hopefully inexpensive as the "real" cause for it not starting now.