What was special about it? Were the terrorists upset by the music of Eagles of Death Metal?

In case you haven't heard, Bataclan was until September owned by Jews Pascal and Joel Laloux and had been for 40 years. Previous owners reported that the venue has been a target for anti-Zionists as they often held pro-Israel events. One extremist group called "army of Islam" has threatened the place in 2011 because it's (sic) owners were Jews (from wikipedia).

http://www.i24news.tv/en/news/international/92438-151114-was-the-bataclan-targeted-for-jewish-ownership-and-support-for-israel