Usually I wouldn't, but there was

• a clear claim made
• that I can disprove to the necessary level of precision
• based on explicit deference to physics

So it's not impossible that MysTerri will retract this particular claim, and that's a decent hook for doubting the rest of the theory. Other responses include accusing me of not being an expert (or lying), renouncing respect for physics, or going content-free.

Also, I'm not sure why you reply here rather than in private, given your reasons.