I don't think you are alone OP.
I think everyone on this forum has experienced the very same thing from our relatives and friends but you must stand firm in your truth and never deviate from it.

My technique for dealing with this problem is to always be calm and never bring these subjects up but if they are brought up I will give my take on the subject which is backed up by incontrovertible facts always in a quiet calm and reasonable way.
Then if they try to get me into an argument over it I will say something like "Well all the evidence points away from what you are saying I can email you the evidence if you want?"
Then I will change the subject or if they are being reasonable I will offer proof but always mainstream media proof they can't ignore or downplay because that is their level of understanding.

But what you must always keep in mind is that these people have been brainwashed and it will take more than facts to wake them up, be gentle with them and treat them as you would a mentally ill person and always remember these are just scared people that love you and who you love.

Don't give up we will win in the end.