A contract perfectly allows a player to be "asked" to take a pay cut. It also allows for a team to cut the player. However, the terms of the contract that was agreed to say what is to happen if either of those situations happen.
Somehow the entire concept of following the terms of a contract is getting lost in this discussion. The terms are the terms. The player and the team are to abide by them. There is NO term in an NFL contract that says "if the player thinks he deserves more money then he has the right to boycott the team, not go to practices, or not to play". The counterpart would be "the Rams unilaterally lowered the pay of Hekker". Or the Rams traded Jared Goff but refused to honor their guaranteed money to him".
The entire point is for both sides to honor the contract. Otherwise fair and ethical becomes completely arbitrary and all the rules of behavior dissolve.... which they have when it comes to players like Hill and lately apparently AD.