My teenage son is extremely hateful to me for a parental decision I made. What do I do?

I agree with the above poster, more information needed. I will say that if your mom has dementia, she is shortly going to need more care than Independent Living is going to provide soon. Your son is 17, getting ready to go off to college and needing your support? Shouldn't your nuclear family have first claim on your attention?

I see from your profile that your mother lives in an independent living place. How much time do you spend over there? How is all of this impacting your relationship with your husband? How does he feel and what does he think about your son's silent treatment? How old is your son?

I feel that I need more information before I can make a comment about this situation.

As a parent most of know that children often feel put upon or unjustly inconvenienced by our decisions.
They often turn to the other parent or friends to punish us.
As hurtful as it is if you show weakness now you play right your son's hands.
Recognize what he's doing.It's called manipulation.
If he turned to his dad so be it.Let him know that's fine but you do not regret your decision.

taking care of someone and being around someone with dementia is hard when you are an adult but add in all the teenage drama and hormones on top of that it's really a lot to adjust too. it also may be hard for him to see his grandmother that way and it may be hard to see you struggling. teenagers like to pull away and hide in on themselves he may be leaning toward your husband because he feels like you have enough on your plate as it is. keep in mind that right now he may feel like everything is out of control witch makes teens act out in a hateful manner. try setting aside some time just the two of you. maybe some holiday shopping or maybe ask him to teach you how to play one of his video games. he just needs to know that even though your focus is on your mother you haven't lost focus on him either. give it time and i'm sure he'll come around.