Plus the X-men were traveling all around the world so the time doesnt really track. You are right in that if Storm turned on tv, Genosha wouldnt have...
His state of mind also plays into his action as he just saw Genosha massacred by a bunch of sentinels. I dont think his actions were self defense but...
TBF the only telepaths we've seen her interact with were Maddie, who didn't like reading people's minds if they didn't present an immediate threat or...