I don't normally think "rules are rules" is much of an argument. Rules exist in contexts, and they have different rationales. For instance, most of us would be rightly pissed off if we were ticked for jaywalking when no cars were around. We also tend to think it's stupid when athletes get DQ'ed for things like minor uniform violations (e.g., a colored sports bra showing underneath a singlet).
That said, I don't think this is the kind of rule that you can ignore. It's central to the competitive structure of the sport, and it actually affects strategy. Knowing that a bad step on the curve can end your race means that smart athletes are careful. I think this is more like a thrower accidentally stepping out of the front of the circle after clearly completing a good throw.
That doesn't mean I think a DQ in this context is a good rule. At least the thrower only scratches one throw for a bad step, but losing your entire race is pretty draconian. I think there are a lot of ways it could be tweaked:
- You could say intentionally stepping over is a DQ, but if it's inadvertent, then the officials have discretion to assess a time penalty (one second per step?) so long as no advantage is gained.
- You could even say that up to three steps, as long as unintentional, are fine, since geometrically there's probably no way to run shorter than the total distance just stepping briefly inside and then outside of the rail.
- You could also have a rule where officials have discretion to rule "no advantage" so long as there's no protest. I actually think it would be good for sportsmanship if a norm developed that people are expected not to protest unless they think they were actually harmed by the violation. Sort of like how everyone likes to see soccer teams kick the ball out of bounds when a player for the other team is injured, I think people would really applaud the second place guy who says, "yeah, I could've talked to the official and gone home with the title, but the other guy deserved it."