I hate when idiots say that builders are waisting the team's time, and should fight, and then go on to destroy their equipment.
Other players do not exist to feed your multiplyer. Each player helps their team in the way that they think best. If you think that fight/die/spawn/fight/die/spawn/fight/die/spawn is best, than do that! But don't destroy people's equipment because you are to stupid to see the benifits of planning, and building.
This problem will never stop untill action is taken against it. Untill the bans start rolling, the griefers will continue to hinder their own team by destroying friendly equipment.