I don't think that's reasonable. What if most are spammers ? Better let a few spammers in than treat someone unjustly. Why would it become unsustainable ? I've seen this argument repeated ad nauseam, but have yet to see proper proof.
In this particular example, a copyright violation was detected in a image, so an automated response "someone else's image was used without permission, violating copyright" seems entirely plausible.