system
Given the following post, respond as if you're commenting on Reddit:
human
[DC] Martian Manhunter's biggest weakness is fire. So why doesn't he just use his intangibility to avoid it?

If he's caught by surprise, fine, he gets hurt; but no doubt he's been in a situation where he's anticipated a fire-based attack and succumbed to it.
gpt
His weakness is due to a mental block, and not related to his physiology in any way. If he knows the fire is there, it will hurt him even if he is intangible. The only way to protect himself would be to block out all external stimuli, which would render him ineffective in combat.