I have used Gordon’s book many many times. Using the rituals does not offend the spirit at all. Even though I have a really good relationship with a couple of spirits, I still use ritual 1 when doing a formal petition.
Look at the ritual as a business meeting. On your first petition, the spirit does not know you and you do not know the spirit. You do your petition, there are some neutral third parties there (angels, view them as accountants or attorneys or whatever), the spirit looks over your petition and decides if he or she wants to work with you. The angels cannot make the demon want to do business with you and vise versa. You state your terms and if agreed upon, then you may potentially have a new business partner so to speak.
After the first initial success, everybody is happy, magician and spirit. You do some more business together, properly doing the ritual for the petition, but after a couple of times, it becomes more than business. You get to know each other. You start building a personal relationship.
After a while, you become close. You go out for drinks, go to each others houses for dinner, get to know each others families, etc… You may even do a business deal on the back of a cocktail napkin, but at the end of the day, whether you are working with a new business partner or spirit, there is still a formality. All contracts in the real world or petitions in this case, still get done in writing, no matter how friendly you have become.
It is not that you are afraid that you are going to get screwed over, quite the contrary, you know that you will not once the relationship gets that strong. It is just what it is, a formality, nothing more, nothing less. As far as having the angels during the ritual, like I said before, it is a non event. Now if you go into the “meeting” guns blazing saying things like “I brought my angel backup, do this deal now” or if you go into the ritual hostile or afraid, things may not go so well.
It comes down to intent. Treat the spirits with respect just like you would if you went into a regular business meeting and chances are that you will start building a foundation for a great relationship, business wise and personally. At least this has been my experience.