  Since the shooting of Black teenager Michael Brown by White police officer
Darren Wilson in Ferguson, Missouri, the protest hashtag #BlackLivesMatter has
amplified critiques of extrajudicial killings of Black Americans. In response
to #BlackLivesMatter, other Twitter users have adopted #AllLivesMatter, a
counter-protest hashtag whose content argues that equal attention should be
given to all lives regardless of race. Through a multi-level analysis of over
860,000 tweets, we study how these protests and counter-protests diverge by
quantifying aspects of their discourse. We find that #AllLivesMatter
facilitates opposition between #BlackLivesMatter and hashtags such as
#PoliceLivesMatter and #BlueLivesMatter in such a way that historically echoes
the tension between Black protesters and law enforcement. In addition, we show
that a significant portion of #AllLivesMatter use stems from hijacking by
#BlackLivesMatter advocates. Beyond simply injecting #AllLivesMatter with
#BlackLivesMatter content, these hijackers use the hashtag to directly confront
the counter-protest notion of "All lives matter." Our findings suggest that
Black Lives Matter movement was able to grow, exhibit diverse conversations,
and avoid derailment on social media by making discussion of counter-protest
opinions a central topic of #AllLivesMatter, rather than the movement itself.
