Are you fucking kidding me? That's literally the exact thing that you're saying.
Them: Here are Biden's stances, and I consider them inexcusable"
You: Actually, they are excusable because lists a bunch of stuff Trump did
If that's not what you're saying, then go ahead and explain how Biden's actions are excusable, why supporting him is defensible, without doing a whataboutism by bringing up Trump doing the same thing. As the other commenter requested.
I swear, whataboutism is just something y'all made up where the only rule is "I'm always right." What a load of bull.