I think you need to clarify 2 concepts/definitions, agnostic of real world events.
1) fake news: a recent phenomenon where fraudulent/fictional/completely made up literature is peddled as legitimate news. This is then distributed on steroids via social media. It uses unsuspecting people to transmit this.
Bias in news. This is an older problem and involves how news is presented and what spin is put. In the worst case it is deliberate in order to support an agenda.
For the second one, he was not mocking the reporter's disability. He was mocking the reporter for pulling a story and the impersonation he did is Trump's standard impersonation for a flustered, bumbling person. There is multiple video of him doing the exact same action to able bodied people - from Ted Cruz to military generals, and all sorts of others.
Not only that, but the reporter's disability is nothing like the action Trump did. The reporter actually has frozen/locked up joints e.g. almost the exact opposite of what Trump did.
So, either Trump knew of the reporter's disability and wasn't mocking it (completely different actions), or he didn't know of the reporter's disability (and therefore couldn't have been mocking it).
In either situation, Trump wasn't mocking the reporter's disability.
Unfortunately a freeze frame from the video of Trump's movement matches a still photo of the journalist, hence the belief that he was mocking the reporter's disability.
And this is why people say the media has a well known Trump bias.
1) fake news: a recent phenomenon where fraudulent/fictional/completely made up literature is peddled as legitimate news. This is then distributed on steroids via social media. It uses unsuspecting people to transmit this.
Bias in news. This is an older problem and involves how news is presented and what spin is put. In the worst case it is deliberate in order to support an agenda.