In my 50 years on this Earth, I have yet to see someone begin a sentence with “I’m sorry, but…” and actually be sorry about anything. Before you start a response that way, pause and ask yourself why you felt the need to include such a preface. What is it about your reply that made you feel it necessary to provide such a disclaimer?
In my experience, “I’m sorry, but…” is most often a phrase intended to make someone feel better about saying something rude and uncalled for. Sure, there is room for the occasional exception, which is why I suggested that you pause and question yourself before saying it. The idea isn’t to avoid saying something, it is to be fully aware of what you are saying and why.
Never forget that I love you, and that excludes no one.