You are exactly saying what I thought you would say. What aggressive spirit are you talking about?
For your information .. North Indians never protected SouthIndia from being plundered. Most of the moghal armies that plundered rest of India was made of North Indians.
If SouthIndian temples stand today that's because of our spirit to defend them and resist foreign invasion.
What north Indians did was ..
1. Invite alien muslim invader to attack his neighbouring kingdom
2. Command Muslim armies against his own brotherly kingdoms (Who commanded Akbar's armies? again?..)
3. Fall one over another to pay tributaries to the Sultans of Delhi...
This attitude was first demonstrated by the north Indians when Ambi sided with Alexander and helped him to fight Porus. That's your history deal with it..