You don't know/understand something. Do you politely ask for an explanation or do you attack/insult due to frustration? Why?

i ask for an explanation, i dont like to be rude

[ The frustration-aggression hypothesis was proposed by Dollard, Doob, Miller, Mower, and Sears (1939). ]

I'm always open minded about anything I don't understand---but that doesn't happen very frequently.  I learned in graduate school that it's advantageous to become an expert in something before discussing it.  

Fortunately, that is a lot easier to accomplish than most people think.  Knowing more about the topic than 95% of the people in the discussion one is involved in is not a particularly high bar to get over.

I think people who attack are those who cannot defend their position because they don't know what they are talking about.

The ones who want to know something, usually do not attack.    It's the one's who don't want to hear anything that attack.