You’re in a tough position. With the right, only the lunatic fringe believed in Birtherism, so mainstream right of center journalism could either condemn it or skip it all together.
But as you point out, and is confirmed by the comments section so far, to be a lefty today is to be a Russia Truther. There are basically no exceptions worth noting. You’re going to have to toe the line or simply avoid discussing it.
Sadly, you’re probably noticing this is starting to apply to all of your pieces. Your primary audience is sick and tired of you telling them to dial it back a notch and wipe the foam from their mouths. They’re only interested in full-bore lunacy, which you’re too rational to deliver to them.