Police Commissioner William G. Gross doubled down yesterday on his fiery criticism of an ACLU lawsuit over the city’s gang database, saying through a spokesman that safety of neighborhood residents remains his “top priority.” “Commissioner Gross is passionate about protecting the residents of Boston, and that will always be his first and foremost objective,” said department spokesman Sgt. Detective John Boyle. Gross slammed the ACLU in a private Facebook post Saturday, saying the “paper warriors” — by targeting BPD’s anti-gang measures with a lawsuit — are ignoring the “atrocities” by the ruthless MS-13 gang. Many of those gang members are...