Is Intego's Mac Internet Security X9 dangerous to use?

I would not use that. It is unnecessary.

Users have also reported problems here and uninstalling Intego resolved the problems

Rule 1 of Macs is don't install garbage. "Intego" is garbage.

Installing Intego's "Net Barrier" and "Virus Barrier" products on a brand new Mac containing little more than one minimally configured User account resulted in the worst performance degradation of any similar product I tested. No knowledgeable Mac user would consider it even remotely acceptable.

Your Mac already includes everything it needs to protect itself from viruses and malware. Read Effective defenses against malware and other threats.

There are no advocacy groups that lobby for the lack of a product. There are only enormously entrenched interests desperate to assert their continued relevance in a post-Windows PC era. The "anti-virus" industry is a corrupt, filthy, multi-billion dollar behemoth with major players who are not about to fold their tents and go away just because the epoch in computing history characterized by the unchecked spread of "computer viruses" has ended. Draw your own conclusions from the fear they seek to instill in their readers.