I'm going to separate this statement from the background of the author to focus on the important part.
The part that struck me as incorrect right off the bat was, "About seventy-five percent of Muhammad's biography (Sira) consists of jihad waged on unbelievers."
There are 164 verses in the Koran that deal specifically with jihad, not including those where Mohammed voiced his opinion of those that choose not to go on jihad, the rewards form heaven for jihadists (not sure if that is really a word), or where it is used as a generic word for "victory".
The statement claims that 75% of all verses in the Koran are about jihad, but there are more than 219 verses in the Koran.
Here are the 164 Jihad Verses: K 002:178-179, 190-191, 193-194, 216-218, 244; 003:121-126, 140-143, 146, 152-158, 165-167,169, 172-173, 195; 004:071-072, 074-077, 084, 089-091, 094-095,100-104; 005:033, 035, 082; 008:001, 005, 007, 009-010, 012, 015-017, 039-048,057-060, 065-075; 009:005, 012-014, 016, 019-020, 024-026, 029,036, 038-039, 041, 044, 052, 073, 081, 083,086, 088, 092, 111, 120, 122-123; 016:110; 022:039, 058, 078; 024:053, 055; 025:052; 029:006, 069; 033:015, 018, 020, 023, 025-027, 050; 042:039; 047:004, 020, 035; 048:015-024; 049:015; 059:002, 005-008, 014; 060:009; 061:004, 011, 013; 063:004; 064:014; 066:009; 073:020; 076:008
Do you have a different list that shows 75% of the Koran?
BTW - Your doctor isn't the one that came up with the figures. He is just repeating the conclusions of Bill Warner - a well-known crusader against Islam (Citizen Warrior Heroes: Bill Warner).
I'm going to throw you a bone. If you really want to make a point about how Islam deals with no-believers, you need to look at the Qur'an in chronological order. That means that Surah Al-Taubah (Chapter 9) is the next-to-last revelation of Allah to Mohammed - hint, hint. Surah Al-Nasar is the last one, but it is mostly empty verses in regards to non-believers. The Qur'an is arranged from longest to shortest in chapters, not in chronological order, and it has a lot of repetition. Later revelations overwrite earlier ones.
Now, I'll throw out a verse for you to ponder, since you said that you have active Muslim friends, but that all of the Muslims are looking to deceive non-believers.
"Believers, take neither the Jews nor the Christians for your friends. They are friends with one another. Whoever of you seeks their friendship shall become one of their number. God does not guide the wrong-doers." - Qur'an 5:51