After that I vowed that there would be absolute clarity on who did what on these kinds of flights.
Absolutely agreed. I too have had bad experiences, because I was shy to instantly and completely take over for fear of hurting feelings. Several times I waited too late, and too much extra effort was required to fix it. After that, I feared being the more experienced pilot in the accident, than hurting feelings.
Now, it's a thorough preflight briefing as to who will do what, and if I have decided to takeover, I will be the only one controlling the aircraft until further discussion.