I believe that the majority of mainstream papers were for remain. I have not analysed readership and reader crossover and so this could be a flaw. Completely happy to be corrected on this.

Lets say for argument it was 50/50. I could definitely understand why people might have the (in this example, incorrect) perception that the majority of newspapers were for remain. As papers are seen as part of the establishment, and the non-newspaper establishment was so heavily remain, it could easily bias your perception of coverage.

"So facts don't matter only what the presented image of what the "majority" thinks?"

Facts do matter, I just believe that the majority have this view of Brexit news coverage for a variety of understandable reasons.