By Gerry Shih SAN FRANCISCO (Reuters) – Twitter Inc encountered a user revolt for the first time as a public company after it tweaked its block function on Thursday, prompting an outcry from those who said the new policy empowered perpetrators of online abuse. Twitter said Thursday that the change was meant to protect victims of harassment who wanted to filter out abusive messages but feared that the act of blocking a user would prompt retaliation. Responding to a wave of criticism, Chief Executive Dick Costolo said on Twitter Thursday evening that the new features were widely requested by victims of abuse. Just ignore them theyll stop is a dangerous thing to say to bullied kids a dangerous thing to say to stalked/harassed Twitter users, wrote @red3blog, another user.