ISIS said they killed 1700 in tikrit and pardoned Sunnis.
Regarding the poor treatment that Shias directed at sunnis? They'd even torture people who had names such as 'Umar', 'Abu Bakr' or 'Uthmaan' and 'Aisha'. Many people who have been abused have spoken out about it, so have many people who have had their childs killed at the hand of shia death squads. That Shia dude called out for his followers to murder and fight against the ISIS. Terrorism fighting terrorism.
Heres an article I found:
http://news.bbc.co.uk/1/hi/world/middle_east/4719252.stm
Videos:
More sunni deaths:
http://guardianlv.com/2014/01/what-is-happening-in-iraq-14-men-killed-by-unknown-death-squad/
More sunni deaths:
http://www.rferl.org/content/bomb-attack-baquba-iraq/24989145.html
Sunnis treated harshly:
http://www.cbc.ca/news/world/shias-dominate-sunnis-in-the-new-iraq-1.1269416
Sorry buddy, but this is non-sense used by extremists to drive the country towards a sectarian war.
Just take this one for example:
14 Men Killed by Unknown Death Squad in Iraq
It seems simple enough, but that black and white explanation does not explain why there are many Sunni militia men fighting alongside government troops against Sunni insurgents right now. One answer could be that not all Sunnis are radical and they support the government because they want stability.
These attacks also do not explain why the 14 Sunni men were recently abducted and executed by supposed al-Qaeda militants dressed as government soldiers. There is currently very little information on who the slain men were (eight of the 14 were from the same family). There is no information on who their abductors were besides the fact that they were dressed in widely available military uniforms. Were they Al-Qaeda affiliated terrorists dressed like soldiers? Shia militants dressed like soldiers? Or, maybe they were actually soldiers.
Al-Qaeda has been known to carry out attacks against Sunnis, and this could just be an example of an internal feud. Equally possible is that the men were killed by a non-government Shia death squad in a revenge killing. Just as equally possible is that it was an actual military death squad.
Until more information comes out, it is impossible to make a definitive judgment on who is responsible for the deaths of those 14 men.
And I can tell you confidently that many many Sunnis were killed by Al-Qaeda in Anbar (Sahwat) because they were siding with Al-Maliki. Just a week ago the son of the Sahwa tribes was killed in Anbar by Al-Qaeda. And even if you don't want to take my word for it, the article you posted was clearly theorizing, but made clear that it could very well be Al-Qaeda doing it.
It's just the typical propaganda, most of which if not all of it are really mere lies, that are meant to gain support for extremists among moderate Sunnis. There is no real sectarian war going right now, and actually Al-Maliki fought all the Shia militias and dissolved them and put them in prison, which is why the real sectarian war (that was triggered by destroying the Imam shrines in Samara) has ended pretty much completely in 2008.
I posted earlier a part of a TV interview with one of the Sunni members of the main Sunni party in the parliament. She was asked about her opinion about Al-Maliki and she said "personally I don't think there will be any Shia PM as kind to the Sunnis as Al-Maliki is". And yes she's from the main and biggest Sunni list, and was the first women on the Sunni list for this elections as well. But she also said that the party stance is different on him and that she will support the stance of her party even if she doesn't agree with it personally.
Believe me there is a lot of propaganda going trying to trigger a civil war and feed extremism in the region. Most of which are pure lies though.
However, what ISIL did by killing all the Shia prisoners and letting everybody else go was really disgusting. Hopefully it doesn't lead to a backlash against the Sunnis, and I don't think it will.
EDIT: Just noticed the date of that BBC article was in 2006! Dude, you're trying to justify something done now because of something that happened in 2006?! Under completely different circumstances?!
I don't even think Al-Maliki was a PM yet at the time!