1- an old woman used to throw trash over Muhammad PBUH every day while he went mast her house during his days in Mecca, he never responded aggressively nor he asked anymore to harm her. when she fell ill he actually went to attend to her and that actually changed her world and she embraced Islam.
2- Arabs pride themselves for being the speakers of the most rich & superior language i.e. Arabic and thus used it to express themselves in the most eloquent way, if they decided to insult someone they used the same power of their Arabic and so did a poet who would write and sing parodies and phrases that were utterly disgusting and insulting to Muhammad PBUH, when word reached the prophet PBUH, he did express displeasure but didnt order anyone to go and kill that poet. As it happens later on the same blasphemer became Muslim later and then wrote songs in Muhammad PBUHs praise.
Examples are many, when the children of taif threw stones at Prophet and when people would put camel guts over Him during prayer times in Mecca, even at the beginning of Islamic preaching he had Hamza & Abu Talib as his uncles who were famous noble knights but he never asked anyone or allowed anyone to seek revenge and punish someone over physically or verbally assaulting and insulting the Prophet PBUH.
Just consider for a second that the 2nd great Caliph Omar before embracing Islam, even set out to kill the Prophet and beat up his sister and her husband as they had become Muslims, now how can this be less serious than verbally insulting the Prophet? But as the history tells us, Omar came out of his sisters house a changed man and offered himself to the Prophet. Any other Muslim, of that time, if he had the same sort of ignorant and misplaced zoolatry of Qadri would have killed hazrat Omar earlier or even when he came to the place where Muhammad PBUH was known to be preaching his followers.
The point is , if we will draw our weapons and start killing people who are insulting Islamic personalities, books and the practices then we are pretty much negating the very meaning of Islam , I.e. peace to all and submission to Allah and the claim about respecting and tolerant towards others.
I hope the pro-execution zealots dont bend the above examples into something out of context and spirit and justify te murder yet again.