You said foreparents would have accepted death to converstion,,,,,,
Whats this logic man if somebody coming to you and guiding you the right do you accept it or you say ill about it.....???
By the way Islam was spread by proof and evidence, in the case of those who listened to the message and responded to it.
So whoever didn't respond they keep on worshiping idols and following their own faiths...
Finally i would say that we are very much thankful to our ancestors that they willingly accepted the true religion and we feel pride to follow their footsteps.
