The Hathaway family was among the most ancient witch families around the world and were the actual founders of the society. Despite this fact, Mike couldn't care less about the quarrels with the hybrids or their future plans. That said, there was one thing he couldn't tolerate and that was his family's secret being out in the open.
His family didn't die to cryptids or to natural causes, they were killed by something ancient whose name had been lost to time before the first human learnt how to speak. Something that needed to be contained at all costs.
Due to Uriel's age, Mike knew he couldn't possibly be the one responsible for what happened to his family, but he couldn't afford to let someone disclose the ancient language to the public and putting everyone and everything at risk.