First of all: if I am 20 meters beeline or less near an archer, I want to be able to charge him and take him out. Because he is an easy target for me (rule Nr. 1, always go for the easy targets first, unless they are peasants), and they can deal a lot of damage (rule Nr. 2, engage the dangerous opponents first.).
It's the same reason why only retards attack the def tank in MMORPG-PVP (infantry, with or without shield, but well armoured), instead of attacking the vulnerable damage dealers (or healers, who have no counterpart in cRPG). Time is an important factor. You need a longer time to bring down a good infantryman than a good archer, and during the time I need to kill the infantryman the archer can attack my team or me CONSTANTLY. If I attack the archer first these constant attacks are stopped, and the enemy infantryman needs to walk up to someone to be able to attack.
So much to "simply attack other targets.", it is the much less intelligent option to do, and yet you were forced to do so by roofcamping.
And just to add to the "roofcampers are ineffective, anyway"-argument: bullshit!
I don't know how offten I witnessed in spectator mode how a group of Byzantines sticked together and hacked their way through the enemy team. After the first big melee was over, there were usually like 20 of the Byzantine's team and perhaps 13 enemies left. Which is a good starting condition for a Biyzantine victory. But the few remaining enemy infantrymen usually were to be found under the enemy camper roof, probably BECAUSE they were there and received covering fire from their teammates. Often enough I saw how three or four random roofcampers and two or three enemy infantrymen on the ground were enough to kill a Byzantine group of equal or even bigger size, who were teamplaying as good as possible. Simply because those roofcampers were still immortal at that moment and could concentrate on shooting the enemy.
If you are about to lose a round, gather under the roof where your campers are, and you have good chances to turn the tables.