Fencing

It's a national team, therefore they're representing their countries in an official capacity, regardless of their personal stances. It's more akin to Nazi Germany sending a team to the Olympic games and the controversy that surrounded that. That's the unfortunate nature of flags and sports, but it's how it is.

Edit: It appears the Russian fencer was participating as a neutral participant and not as a member of a Russian sponsored team. That makes it objectively unsporting on the Ukranian fencer's behalf, however subjectively I at least understand the problem. Just because the Russian fencer isn't participating as part of their national team (because their team was not allowed to participate) doesn't mean they aren't otherwise that team's fencer and are still, unofficially, representing their country.

As far as I'm aware, Russians are only allowed to compete if they are unaffiliated with the military. In a twist, the Russian competitor was also post-emptively disqualified from the competition because a picture of her supporting the Russian military was discovered (which is against the conditions for Russians to fence). If that picture has been uncovered before hand the Ukrainian would never had to fence her and wouldn't have been black carded.

Also, she did offer to tap blades, which was the defacto solution during COVID, so it wasn't a complete snub.

I find the politics of this situation very fascinating.