Question

I could go on indefinitely about brutality and lack of consideration. The word indefinitely, as used in this sentence, suggests that Bertie is being dramatic bored of the topic changing his mind calm and calculating

Answer 1

being dramatic

Indefinitely means that something could last forever, so Bertie is being dramatic by saying he could speak about this topic without ever stopping. Clearly the topic means a lot to him and he has many thoughts and opinions on aspects of it.