There's an academic consensus that exposure to violent media increases violent and aggressive behavior, eg[1][2].

Needless to say, this is very widely disputed and fought over. It's possibly more controversial than climate change.

However, it's quite widely studied[3], and the consensus position is fairly settled.

[1] http://www.jaacap.com/article/S0890-8567%2809%2960387-7/abst... (This is a meta-study)

[2] http://psycnet.apa.org/psycinfo/2014-41977-001/

[3] http://scholar.google.com.au/scholar?hl=en&as_sdt=0,5&q=impa...