I think it is incredibly hard to not tilt one way. After all, organisations are run by humans and we all have our own leanings. It is very much possible when we hire people those leanings bias us towards a certain ideology and we may hire like minded individuals. Also, people who don't fit the ideological tilt might feel left out and may leave on their own. So, over time a media organisation will come to represent one side more.

This all in addition to the biases that can come from the owners/company bankrolling the media house.