I'm doing the wildcard quests. Yes man asked me if I wanted to ignore the Brotherhood and the Boomers (whom I intend to join) and I said yes, thinking he meant ignore as in leave alone/not attack and that I saw no other option. And I killed Mr. House before activating the Securitron army. Can I still activate it?

whoops, wrong forum...

Yep. http://www.gamesas.com/index.php?/topic/1154402-help-i-think-i-screwed-up/