Truth is a very fluent concept, unfortunately
Yes, news should always tell the truth, of course, but it is so easy to (accidentally) inject bias. You could simply spend a minute more on one interview than another and be biased
Journalists should always strive to be as closed to unbiased as possible, and indeed always try to report the truth in a truthful manner
Tell that to fox news and co
This also implies that news organizations must be independent and should always be funded by independent government organizations, not some rich billionaire