I already use this after they login i just don't want the activity page to exist at all and being the default when someone goes to homepage when not logged in.

Simplest way would be registering of a custom index page that just forwards to the group profile page. Create a plugin with the following code in start.php:

<?php

elgg_register_event_handler('init','system','group_indexpage_init');

function group_indexpage_init() {
    elgg_register_page_handler('','group_indexpage_index');
}

function group_indexpage_index() {
    
    // Enter in the following line the group guid instead of placeholder; you'll find the group guid in the group profile page url
    forward('groups/profile/GROUP_GUID');

    return true;
}

Hi Thanks for the suggestion. 
Is working fine for me