Among various things the one that annoys me the most is:
Having a preconceived notion about a particular technology and trying to convince programmers why that tech is bad without any evidence or proof.
I have encountered this problem many times. There are people (non-programmers) who never get a chance to evaluate a technology, but they somehow develop a negative perception towards it. The worst part is that they try to discourage everyone else in the team by portraying negative things that aren't true and obviously can't be proved with benchmarks and evaluation.
A real conversation. I met someone at a conference and that person was into product marketing:
They: So, what tech are you using to build your product?
They: Really? But that's a language just for PoC right? Just rewrite your codebase in python. It's age-old and battle tested.
me: Ok. 🤯 Let me grab some coffee! Will see you soon.
I still have no idea how to deal with these people. Maybe someone can advise?