Hey there.
A very common and well known tactic for all objective-based game modes, especially Domination and Headquarters, even better in hardcore versions. If you can find a place where you are protected AND able to see the objective then you can protect it as best as possible then when most/all of your team is dead or unable to get to the objective, you can blow the team up JUST BEFORE they cap the objective, do NOT do it too early otherwise you end up wasting points that you could have gotten by waiting for them to cap it and stalling them.
If I am playing in a group in any CoD game, I make sure that at least two people have C4 in their loadout specifically for this so they can cover the objectives and, in my experience, the enemy team get VERY frustrated by it if you keep it up because every time they try to cap it, boom, and when they come back (you should be quick enough to replace the C4), boom again. It's excellent for demoralising the other team and a brilliant tactic to push you towards victory.
Cheers!