From the story he just assumed that his friend dropped him because of social class, but that might not even be the case. If I were in his position I will ask questions before deciding on what to do next.
Personally, I feel like watching over refreshments is far more important than just bein a man in suit, it's a very hectic job and it takes trust to be asked. I am saying this based on experience, nothing stresses a celebrant more than seeing refreshments being mis-shared, so you would be doing them a big favour by making sure everything goes well.
If this wasn't this case and his friend dropped him because of social class, he should've still gone to the wedding (arriving late), or just attend the church ceremony. Why? They might reconcile in the near future, however, the opportunity is gone to witness the union.
If someone is really your friend, you won't jump into conclusions. Unless you were uninvited, don't skip entirely.