They are many different points of views on VideoGames in general, and both use any piece of Evidence that can be found to use it for their purposes to spread the word of their ideals. Another thing to make note of is that you can't fit one group as a 'ism' they are differing viewpoints in a singular 'camp' so to speak. For the extreme parts of the Anti-Game comunity the Sources that they used are questioned, but if you dig far and hard enough there is a possiblity you might find the same thing on the Pro-Game 'side'.
The effects on the brain are both good and bad, but it only becomes bad when you get to the extreme levels. Before you get to that, it seems to be only positive.. This is a complex debate, with many standpoints hpoefully this site helps you understand.
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In all, this is a complex issue with legitamate arguments on both sides.