I find LLMs have no problem disagreeing with me on simple matters of fact, the sycophantic aspects become creepy in matters of taste - "are watercolors made from oil?" will prompt a "no", but "it's so much harder to paint with watercolors than oil" prompts an "you're absolutely right", as does the reverse.

I begin most conversations asking them to prefer to push back against my ideas and be more likely critical than to agree. It works pretty well.

Not proud to admit that I got into a knockout shouting match with ChatGPT regarding its take on push vs pull based metrics systems.