Should this have been dative rather than accusative?

Question

Am I right in thinking that the dative, "niemandem" should have been used here?

https://scontent.xx.fbcdn.net/v/t1.0-9/20245739_822304037925478_3033354218549894808_n.jpg?oh=dc1acf647abbc53f6c6ede4e0efda730&oe=5A0AC11C

"Du brauchst niemanden etwas zu beweisen."

Answer 1

Yes, it is dative "niemandem", not the accusative "niemanden", as it is the indirect object, not the direct object "to be proven". The form "niemand" without special ending is technically also possible in both, dative and accusative.

Du brauchst niemandem etwas zu beweisen.
Du brauchst niemand etwas zu beweisen.

http://www.duden.de/sprachwissen/sprachratgeber/deklination-von-niemand

Answer 2

You're right about that. The dative is right here.

Btw. Der Klügere gibt nach, bis er der Dumme ist.