There's a possible reason why your Facebook and Twitter pages are filled with the ALS Ice Bucket challenge more than posts condemning the Islamic Militant group ISIS: it's called the "spiral of silence."
The spiral of silence is defined as a reluctance of one to speak up about certain issues if their views are not widely reciprocated. This can happen with in-person interactions with family, friends, and co-workers, but also with social media, where the popular opinion is that people feel more liberated to voice their opinion.
In a study conducted by the Pew Research Internet Project, the group found that more people are willing to speak about controversial issues in person than they are to speak about the same issue on social media. They also found that contrary to popular belief, people do not feel free to express their opinoin on social media about controversial issues more than in person, and especially if they think people disagree with their opinion.
This may explain why a quick examination of Twitter will find that ISIS was tweeted 3,955,467 times in the past 30 days, compared to ALS, which has been tweeted about 6,041,571 times.
The Pew Research report also found that people are selective of their response on issues for various reasons including their confidence in how much they know, the intensity of their opinions, and the level of their interest.
Pew Research Center conducted the survey of 1,801 adutls, aged 18 and older, between August 7-September 16, 2013. The margin of error is +/- 3.3 percentage points.