I'm fine with whataboutism when it's used to expose hypocrisy rather than excuse bad action.

Is there an example where it is not intended to excuse bad action? Sure..

I often hear from major party backers "I can't vote for (politician from one side) because they did or support this bad thing (that has been done or supported by their opposition in the other party as well).

I point such things out in order to encourage them to look at options that don't do or support that bad thing or things similar to it.

Like... I used to live in Wisconsin, and I'd hear a Republican friend say "I can't vote for that progressive liberal, because they support welfare", and I'd say "didn't Walker support Foxconn and give money for a new Bucks arena?" not as a way to excuse either but to point to another option.

I'd hear a Trump supporter say "I've gotta support him because of the second amendment", and I'd put out a quote about taking the guns first. I'd hear someone back in the day say they supported Obama because they were antiwar and I'd point out him violating the war powers act, or that they supported Biden for legalizing pot and I'd point out his record as a drug warrior.

I didn't want anyone to support Romney or Trump, Biden or Hillary, when I said these things. I didn't want them to forgive war mongering or prohibition or gun control or deficit spending just because the other side did the same stuff.

I wanted them to realize both major sides suck.

One that came up a lot...

"I can't vote Democrat because look at what they do to the national debt!"

Have you seen what Republicans do to it?

"I can't vote Republican because I want to stop bombing poor people in deserts!"

What do you think Obama was doing on foreign policy?

If I follow that up by talking about Jo or Johnson, or my local LP peeps, it's not intended to excuse any of the major candidates or their actions for anything.