This whole burden of evidence is sort of funny.
Generally, people who assess evidence for an alternative hypothesis (RM being favored) against a null hypothesis (no favoritism) don't have an intrinsic link towards one of the hypothesis being true. You being a RM fan are going to tend to weigh evidence towards the null and us being Barca fans will tend to weight evidence towards the alternate.
There isn't any science to this. It's all opinions and in the end, neither party will convince the other.
Only if you're being utterly dishonest about the data.
You and I both know that the very least people could do is do their legwork WRT the data i.e. assemble an honest database through one season in Microsoft Excel with relevant links + videos/gifs of the best possible quality showing incidents in question, and upload it to Google Sheets or something. Calls in favour and calls against. Yellow cards, pens given/missed, red card given/missed. It's not hard to do at all. Point is these vacuous fools can't be arsed to do it or are too stupid to realise they need to in order to prove that 'alternative hypothesis' of theirs. It's far far far easier to just send 2-3 links of some calls that went in favour of Madrid/against Barcelona and voila - fact proven.
Nor do they have the slightest awareness of protocols, how RFEF keep track of mistakes, how they hire and dismiss referees etc. etc. And they still talk like they know shit
Hence the only reasonable treatment is to call these people out for the mugs they are, since it is they who are making the utterly baseless accusations designed to tarnish reputation. Based on absolutely nothing, but their hunch. Don't have to look far but the post above.
This whole narrative that the media also L O V E to latch onto is designed to tap into the age old victimhood complex stemming from the results of the bygone eras. It's "Madrid is Franco's club" with a different flavour and seasoning. Nothing more. Zero science and research at the core of the claim and therefore zero value. To be ignored. Or better yet, ridiculed without remorse.