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The referee's decision is inviolable although I see where the referee's tendency seems to favor a team, this will be difficult to prove if the referee is cheating.
Even if the referee makes a mistake, they will not admit it now but after a few years or he has retired then he will reveal all his mistakes, this I saw several referees who have retired admitting to making mistakes.
That's the way it is, no referee's decision can be contested even if their mistake is proven at a later time. Even with VAR technology, referees can still make mistakes and this doesn't only happen in matches involving Real Madrid. I don't blame Real Madrid in this situation, but several big teams including Real Madrid and others often benefit from referee decisions that appear to be biased.
You still remember the Barcelons vs Chelsea match - I don't remember the year, but the referee seemed to favor Barcelona.
If you forget, just remember the mistakes made by the referee in the Liverpool vs Real Madrid match in the last few seasons and this is still new compared to the Barcelona vs Chelsea match.