To be fair no team can beat Real Madrid, until they do which is a shock to the whole world. The only team that can realistically beat Real Madird is Manchester City, aside from that no matter which team we are talking about it doesn't make sense for Real to lose, doesn't matter which part of the world this club is from, stuttgart or not, no team has a chance to win.
But, sometimes Real plays terribly and loses, just a few years ago they lost to Serrif, a team that worth 10 million euro total, and yet it happened anyway, so shocking results do exist in football, same season Real Madrid won the UCL as well. So, do not be really worried about Suttgart, they will lose, and if not then they will be very happy, but it's still smart to bet on Stuttgart to lose.
I disagree with you, like who is Real Madrid that is only Man City that can beat them? Some seasons ago Madrid lost to Shakhtah, I think it ended 3-2 so you can't be saying that. Even in this very state of Madrid with all the big boys they have I still believe that there is a team capable of beating them after all they (Madrid) haven't been able to play as a unit, just running and making some crazy mistakes against teams they're suppose to beat without stress.
Stuttgart can as well beat Madrid, it all depends on how clinical they are in front of goal, converting any chances they have got and if they can get that then they can beat Madrid but betting on Stuttgart against Madrid is a bit tempting but anything can happen, Madrid can decide to go and take a nap and you see them losing to Stuttgart, I don't think anybody would like to take that chance of staking on Stuttgart.