You could, but the forums might not work correctly. Appears some of the actions for the forums already exist.
I would try this first which should remove those actions.
DELETE `sys_acl_actions`, `sys_acl_matrix` FROM `sys_acl_actions`, `sys_acl_matrix` WHERE `sys_acl_matrix`.`IDAction` = `sys_acl_actions`.`ID` AND `sys_acl_actions`.`Name` IN('forum public read', 'forum public post', 'forum private read', 'forum private post', 'forum search', 'forum edit all', 'forum delete all', 'forum make sticky', 'forum del topics', 'forum move topics', 'forum hide topics', 'forum unhide topics', 'forum hide posts', 'forum unhide posts', 'forum files download');
DELETE FROM `sys_acl_actions` WHERE `Name` IN('forum public read', 'forum public post', 'forum private read', 'forum private post', 'forum search', 'forum edit all', 'forum delete all', 'forum make sticky', 'forum del topics', 'forum move topics', 'forum hide topics', 'forum unhide topics', 'forum hide posts', 'forum unhide posts', 'forum files download');
Unfortunately one of the drawbacks to a failure part way through a SQL script run, is some of the install of the forum already completed. So when you go to install it again it may fail somwhere else.
You could try also manually running the forums uninstall.sql from phpmyadmin.