What does referee history has to do with how the outcome of a match would be? This is not one of the things that I can possibly think of while analyzing a match to bet on.
I know it's sound weird, but there are sports bettor who take that into consider. Just like in NBA with referee Scott Foster refereeing with Chris Paul player regardless of the team Chris is in.
https://www.statmuse.com/nba/ask/chris-paul-record-with-games-officiated-by-scott-fosterIf you want to be betting on Real Madrid, it is not bad at all as long as you can afford to lose the money that you are using to bet.
The thing is that if you are fan of Real Madrid, then you might used your emotions to bet on them. However, if the odds are that bad, or if they are the underdog, it's very hard to get against them because you are a fan. Not just in football though, even in other sports, if we involved our emotions if might turn out bad for us.