Bayindir, making his Premier League debut against Newcastle, gave away possession for the Magpies’ fourth goal.
Amorim says Onana, a £44m signing in 2023, “deserves” to return to the starting XI.
“When I made that decision I talked with Andre and that is important for me to explain to the player to understand what I am thinking,” added Amorim.
“Sometimes the player is saying one thing and I understand it’s a different thing, sometimes it is my feeling as a coach that can make my decision more than what they are saying to me. They want to show they are really confident and I can feel the other way. So I have the conversation but it is my decision in the end.”
United’s season rests on winning the Europa League in order to qualify for next season’s Champions League.
The Red Devils will be without Joshua Zirzkee for the remainder of the season after the Dutchman sustained a hamstring injury against Newcastle.
“Joshua is out for the season so he is not going to play more,” Amorim confirmed.
“Let’s prepare him for the next one. It is tough, especially in the moment. He has to be ready now to recover.”
Matthijs de Ligt was once again missing from training, while defender Ayden Heaven has suffered a “small setback” after returning to the squad for the defeat by Newcastle.
Defender Jonny Evans and goalkeeper Tom Heaton, both long-term absentees, returned to training on Wednesday.
BBC News