You've got to stick to the basic safety rules on the track. By making racing unsafe, as this person did, you ruin it for everyone.
If you feel that someone's unsporting behavior on track needs to be matched by your unsporting behavior off-track, then have at it after the race is over. Hell, you could probably turn that into a pay-per-view even and give extra championship points for how well each driver fares in the brawl after the race.
But don't mess around on the track while a race is on.
I still remember that steward at the Canadian GP in 2011, I think, that slipped while crossing the track in a gap of the safety-car train, and almost got run over by a Ferrari, who barely managed to drive around him. That was a scary moment, and I'm sure it had an influence on trackside worker's briefings, about how the racing line gets slippery when wet, and about how you count the cars when the SC is through, and wait for everyone to go by, before crossing the track. Sadly, I couldn't find a clip of that Marshal as proof, that stupid and racetrack don't mix.
You don't walk into the racing line while a race is on, because even under a yellow, people are still focusing on the race, and not on dodging a person that is erratically moving across the track.
I'm not sure how this sprint car culture got to the point, where people are so blasé about safety, that they think walking onto the track is in any way acceptable. People that pull stupid stunts like that need to get race suspensions. If I had a track and an amateur would pull off something like that, they'd be banned from that track for life.