Argument and flattery are but poor elements out of which to form a conversation.

[Widerspruch und Schmeichelei machen beide ein schlechtes Gespräch.]

Johann Wolfgang von Goethe (1749-1832) German poet, statesman, scientist

Elective Affinities [Die Wahlverwandtschaften], Part 2, ch. 4, “From Ottilie’s Journal [Aus Ottiliens Tagebuche]” (1809) [Niles ed. (1872)]
    (Source)

(Source (German)). Alternate translation:

Contradiction and flattery both make bad conversation.
[tr. Hollingdale (1971)]