That I should not speculate on the motives or incentives of groups that I don’t have direct experience with. It causes me to make assumptions that aren’t validated by reality.
Edit: To be clear, I didn’t write the article. My bona fides don’t have any bearing on this because I’m not the one writing articles for the Telegraph suggesting I can predict the actions of mercenary groups. My read is that the author shouldn’t be speculating either (without providing additional information).