I sympathize with you @imaginethat more than you know.

I have two uncles like yours; one is alive and one is dead. Like you, I'm 49 (you are 45). Like you, I've been undermined by family members whom I've confided to about these uncles, where they invalidated my feelings.

Muffling your feelings about your uncle won't change the way your uncle behaves and it won't change the way your family enables him to behave this way. And, it won't suddenly make your family members sympathetic to you -- because you stopped confiding to them about how much his behavior bothers you.

What I did with my two uncles:

My father's brother: I wrote him a letter spelling out EVERYTHING in print to him about how his behavior bothered me. I made him read the letter in front of me because I told him it would be proof that he read and understood what his niece (me) felt. After he read my letter, he apologized. I thought it would change him, but it didn't. The proof? Years later at my brother's wedding, he tried to sexually molest me...again.

My mother's brother: We have VERY different political and religious views. The only commonality we have is for our love of literature and poetry. He's the only person I can quote poetry or prose to, who knows the poet or author I'm referencing on-the-spot. But, unfortunately, he's an asshole. He condemns me because I'm an Atheist and because of my opposite political views. He's still alive but we no longer talk. His other brother who died about a decade ago, was much kinder and more accepting and was my favorite uncle. So, that knowledge may play into why he and I clash.

In both of these examples, I tried to alter the dynamic between my two uncles but regardless of any effort I made, they both refused to change to improve their relationship with me, their niece.

So, my advice to you is what's already been suggested here: set up some boundaries to protect yourself. Set up consequences with your boundaries as Sarah suggested. Set aside your need to placate your family members. To put it crassly, 'screw them.' You are an adult. Your family is not allowed to dictate the circumstances of your quality of life with them esp. where your uncle is concerned.

Do what you need to do, to take care of yourself emotionally. Limit your time with this uncle and any limit your appearance at family functions where he will be. Have a buffer with you (in the form of a person, or a rehearsed response that you can just repeat like a broken record). There's a ton of cognitive therapy tools available to you to use with dysfunctional family interactions. Or, you can just do what I did; walk away and estrange myself from them. They don't support me or even like me, so I've lost nothing by walking away from that toxic group of family members.