From Sensei Michael Mackay, Go-dan
Midtown Karate Dojo,
Occasionally one will witness a disturbing though unintended breach of etiquette when a bunkai attacker blocks each and every offensive move, effectively defeating the person performing kata. Such interpretations make a mockery of the kata, its composer and the student because they portray the kata as ineffective.
At an advanced level, when a kata includes a series of offensive techniques (such as three consecutive punches in fukyugata ichi), an attacker may block the first one or two moves. This helps underscore the "never move back" and "never give up" principles of kata. But in every bunkai the person performing kata must have the final word, whether it takes three consecutive punches or 300. Even when a kata ends in a defensive move, as in fukyugata san, the block must be powerful enough to break the opponent.
The supremacy of kata must never be challenged, even accidentally.
Domo arigato, Hanshi,
Michael Mackay, Go-dan