TMZ has learned ... Vick -- who cancelled his book tour after "credible threats" were called in to several Barnes & Noble stores across the country -- says he refuses to let his haters control his life.
Vick's rep tells us ... "Regardless of the past threats, he has millions of fans around the world and has been receiving countless messages of support. He will continue to keep an active schedule working with charities."
Mike will continue to work with the Team Freedom Outreach (recreation and visitation programs for youth detention centers) and the Veterans of Foreign Wars organization. We're told Mike has security measures in place in case more threats are made and plans on giving cops a heads up before he visits the centers.
"Mike is committed to helping make his community a better place," Vick's rep says ... adding, "[he] is determined to continue his work with charity and helping others."