This is something that I think needs to be addressed. Post your thoughts!
There is a difference between criticism and hating, although the line between the two can become blurred. To me, criticism is generally always good. Hating is generally always bad.
An example of criticism - If you don't learn to mix without auto-sync, you are limited in what equipment you can use and you may miss out on what can be a rewarding part of DJing.
An example of hating - Auto-sync is wack! You're a joke! Buy and use the gear I'm telling you to buy and use or you're pathetic.
Another example of criticism - Your mix wasn't very good, so I would advise that you learn the basics of phrase matching and using levels and EQs properly.
Another example of hating - Your mix is shit! Sell your gear and forget being a DJ!
The other difference between criticism and hating other than the way that the criticism is portrayed is in who/what the criticism is aimed at. Those that want to help people via criticism offer it up as a way to nudge a person in the right direction. Someone that's hating will hate even if the person they're hating on is better than they are, because it's not coming from a logical and honest standpoint. They may be jealous. They may just be trolling idiots.
Criticism is helpful to everyone IMO, as long as it's presented in a somewhat constructive manner. Hating doesn't really achieve anything positive, and my problem with it is that it can create a divide between experienced DJs that have potentially good advice to give, but are somewhat set in their ways, and n00b DJs that are just coming up that would benefit from some guidance. That can lead to those n00bs seeing people with lots of experience as "dinosaurs" that are stuck in the past and then both parties shut up shop and nobody benefits.
I guess what I'm saying is - don't judge a book by its cover. Not everybody DJs the same way that you do. Judge a person by their passion, their knowledge, their professionalism, their mixes, whether they are successfully rocking parties, and whether they sound like they respect the artform of DJing. If you see a n00b going down a road that you feel is the wrong one, say so, but explain yourself. If you're an experienced DJ, think about your own prejudices and whether or not they actually make any sense in 2012. Think whether the advice you are giving is actual good, critical advice, or whether it crosses over into hating, because if you do the latter you are only pushing people away!
That's not to say that hating is never justified, but a lot of venom that's directed at n00b DJs is totally undeserved and is actually counter-productive.