Why so much hostility to newbies?
There are bound to be numerous reasons, but I think, at least in part, it is because those who have been around a while hit a burnout point where when they see the exact same question asked that they have politely answered a thousand or whatever number times before that some begin to respond sarcastically. They think, there's a search function, try using it before asking what has already been asked and answered near countless times before.
Another cause could be how some newbies will be anxious for a reply and ask the same question in multiple forums, most of which are not the appropriate forums to ask the type of question in.
Another, again newbie caused, is on any given day the very same question might be asked, two, three, four, and I have seen one asked as many as five times, in a single day, all in different threads started by different newbies. At some point some members think, the exact same question has been asked today, twice or more times, do you really need to begin another thread asking the exact same question? If so, why? Just to build your post count by starting your own thread and then responding to everyone who posts a message in it? If you won't use the search function all you need to do is watch/read one of the other threads started that day asking the exact same question and you will get your answer and you can respond there and ask followup questions there if need be.
Then there is the one where a newbie will ask something and after receiving a correct response reply saying something like, but my cousins girlfriends brother works with a guy who heard some guys talking on a bus about how one of their brothers lives across the hall from a guy and while listening at his door he heard the guy telling someone else on the phone that's not how you do it and you do it this way instead. That gets old and the next time a newbie question is asked, the sarcasm and venom flows.
Some growers that are hardly more than newbies themselves, but want to come across as old pros will read a question, that in some cases they couldn't begin to answer accurately, but then go on to attempt to make the question, and the person asking it, appear the dumbest ever, as if they were never so clueless and would never dignify such a stupid question from such a stupid person by answering it, and instead make fun of the person, and or question.
I'm sure there are many more reasons, but those come to mind first.