Not getting involved in blog politics, but Arrington/Crunchfund is an investor in Pando, TC is a competitor, the Pando Execs and board likely made a decision based on the competitive environment.

I can see for a generic company with investors A, B, and C; if B decided to get involved with a competitor, the board and execs might make plans accordingly. We've seen this in the seed VC world with express decisions to not invest in competing companies.