The captains of European teams won't wear their - much maligned, because already watered-downed - diversity arm bands. The players of the Iranian national team won't sing their own national anthem. Seems the European players were afraid of the consequences... the consequences being not imprisonment or house arrest, but to lose multi-million Euro contracts or something. Congrats.
Accumulation of yellow cards in past tournaments resulted in some of our best players not being able to play in key matches, so yellow cards do matter.
If you would want to protest against such a decision, the team would have to decide to go home and not play.
We don't have great width in our selection so we cannot like freely take yellow cards just out of a matter of protest, when the entire nation expects you to at least be in the QF and to be a shadow favourites of winning the tournament. That would be very unprofessional.
If they want to protest, they should just go home and not participate at all. Yellow cards are too much of a disadvantage that it simply would not be worth participating if you want to make the gesture.
Or alternatively, teams who have received yellow cards for wearing the arm brands could choose to ignore the yellow card and send the respective players on the field anyway.
What is the FIFA gonna do? Prematurely terminate the match whre this happens? Disqualify the team for the rest of the world cup? This would create an even bigger scandal for FIFA, possibly endangering the entire world cup if such behaviour snowballs. I dare Infantino to go through with it. This is a game of chicken, and so far it is the European teams who have chickened out unfortunately.