Of course it's disrespectful, anyone with half a brain can see he is worth more than 25 million euros, it's a pathetic bid and one United were never ever going accept, Madrid likely knew this and also knew it would unsettle him to the point that he can't be trusted play, what does that achieve for the sake of a few extra million that they can easily afford? It messes with a top players head, and breaks bonds between two top clubs, if Madrid truly value the guy then they should just be fair with him and pay a fee that would be a compromise, say 40 million euros.
Ultimately it's DDG that's suffering and Madrid are the ones causing it, United are rich enough and I suspect stubborn to bench him, or send him to the stands with no issue at all.