Answer 1: Muslims don't "insult" the actions my brother. But they are not following. There is a lot of difference between insulting and not following. But at least every Muslim do follow at some extent. Can't say 100% not following (for majority)
Answer 2: True. If non-muslim "INSULT" Islam, then its a worse nightmare for Muslims. Any Muslim whether he practice Islam or not, he got Iman in his heart of how much weight (ALLAH KNOWS) but it exists. So when anyone tries to Insult Islam in any form, then the same guy stands up and tries to become defence shield for Islam why Because of Iman in his heart.
I didn't wanted to offend you but brother if we think as a Human (no religion involved), even then our Prophet Mohammad pbuh was/is/will remain the best of the Creations of Allah. As Prophet Mohammad pbuh is a mercy for humankind and all the creations of Allah (not for only Muslims but for whole humanity). So why someone as a Human will insult such a Greatest Personality pbuh of all times. Isn't it against humanity.