Of course not. But some are more credible than others. We see it all the time on these forums.
We can make logical judgements based on facts we see or are presented. The above example of the Russian jet for instance. Turkey bankrolling ISIS (that was minimal on western media) but prominent elsewhere. When one outlet provides more information as RT did with the jet incident they become more credible because of the nature of what they are reporting and the information reported.
Same as with the migrants rampages. BBC was silent on it, then lied, then was laconic and eventually when so many instances occurred they had to go with something. Remember the BBC didn't report the Cologne sex assaults until what a few days or a week since they happened?
They were all over certain news reports (RT included) well before. BBC also deliberately chose not to air certain attacks.
All news has an agenda of course it does, but people who hold the BBC now, today and going forward as a reliable and impartial media platform are beyond naïve