Faction protests in "Frost Age 2" are a common thing in the game. When the laws or decrees you issue do not meet the requirements of a certain faction, they will have a high probability of protesting and want to solve the problem. Protest issues can include repealing laws that the faction doesn't like being passed, or working on multiple projects of their choice.
How to solve the faction protest in Ice Age 2
Factional Protests If you are unable to quell a protest before it starts, you will have the opportunity to stop the protest by meeting some of their demands. Generally speaking, you will usually have the following options:
Repeal laws that the faction does not like being passed
Research multiple projects of their choice
Come up with your own strategies to increase their trust (e.g. fund their projects)
If you are on good terms with the faction directly opposing the protest, they may end the protest early without you having to take any action.
This can be a good way to stop protests early, but if passion and poor relations with opposing factions persist, protests will restart elsewhere. The advice is to try to allay the concerns of protesting factions rather than letting your allies solve the problem for you.