The users viewing option on forum home uses this setting:
Admin CP -> vBulletin Options -> Forums Home Page Options -> Display Logged in Users?
Note, this function also controls the listing the the Members Online on the forumhome page.
If you do not want to do this, the only other option is to manually edit these templates:
forumhome_forumbit_level1_post
forumhome_forumbit_level2_post
And phsyically remove this section from them:
<if condition="$show['browsers']"><span class="smallfont">(<phrase 1="$forum[browsers]">$vbphrase[x_viewing]</phrase>)</span></if>