Well, as it turns out, from a quick google search (an actual expert might jump in and correct me because as we all know google is not a cery reliable scientifically accurate source). Polar bears do in fact avoid humans when possible so my statement is indeed true, according to the same sources, they would rather hunt what they are used to hunt aka seals because they run less, they fight less, they look less intimidating and less "alien" than us humans.

Due to human activities and climate change, they are sometimes forced to take more risks by going close to humans to get food but they still prefer to keep their distance unless they really need food.

So no they don't just jump at anything that moves unless they are desperate. It is similar with a lot of other predators as well, they try to avoid people too.