Because they have been told good things about them, just as you perhaps have been told bad things about them. At the end of the day, how any historical person or event is perceived by generations that follow depends on the value systems that prevail in their wake.
The Indian Muslims you speak of relate more with the ideas that fueled these invaders. You on the other hand, relate more with the idea of a static India that suffered under these assaults. Their heroes took what they wanted. Your heroes fought to survive and remain free. There is nothing subjective about it — the events that took place are a matter of historical record. The only difference is what aspect of those events one chooses to belong to.
Understand that if you had been in the place of the Indian Muslims you describe as being in love with the invaders, you too, might have felt the same. I am sure there are many Indian Muslims who either do not feel any great affection for these historical “heroes” or simply accept the events as something that happened a long time ago and have no bearing on present-day India. Similarly, there might be non-Muslims who admire these invaders and look up to them.
What is the way out? The first step of course, is understanding that history cannot be changed. Good as well as bad things happened in the past. None of us would have been here if either of them had not taken place. We are all products of the tragedies and triumphs of the past. None of us can live in denial.
The next step is to take emotion out of this equation. Anger at a dead invader is as likely to change the future as devotion for a dead saint. The future should be built on the foundation of truth. And the people who build this future will be neither Hindus nor Muslims. They will be informed and educated citizens of a modern India.