A few weeks ago I asked the question: Why does everyone [including me] preempt a tactical suggestion with anapology ["I'm sorry, I know this is so tactical but what if ..."].
Seth Godin tackles a closely-related topic:
I was at a gala a few weeks ago (featuring no less than ten speakers). At least 80% of them began their talk by saying, "I know you're hungry, but..." or "I know it's late, but..." or "I know you want to go home, but..." and then apologized for giving a speech.
If your speech needs to be prefaced by an apology ... don't give it.