The Formula 2 champion's McLaren entry made contact with JHR driver Augustin Canapino at the Turn 3 hairpin following a restart, one of several incidents triggered by drivers struggling to bring their tyres up to temperature in a race blighted by caution periods, that also featured a rain shower.
Both drivers continued to the finish, with rookie Pourchaire placing tenth on his return to the series after sitting out the Indianapolis 500 and Canapino taking the flag in 12th.
Following the race, Pourchaire was sent abusive messages which prompted JHR and Arrow McLaren to make a joint statement posted on the latter team's website.
"The past 24 hours have unfortunately provided our teams with a stark reminder about the necessity for respect and civility in our online interactions," it said.
"Social media allows us to engage with our fans around the world, but it is important that we interact with each other in a respectful and safe environment.
"We will not tolerate any form of abuse or discrimination, and those participating in such actions are not welcome in our online community and will be blocked.
"The NTT INDYCAR SERIES delivers dynamic action on the racetrack and incredible access for fans, but we must remember that behind the wheel, the pit wall or the monitor, we are all human beings.
"It is vital that we collectively maintain a safe and welcoming community for all involved."
JHR followed up with its own statement, in which it confirmed "we are working with those affected to identify the individuals responsible, and any violators of this policy will be blocked from the Juncos Hollinger Racing community".
Pourchaire, who switched to IndyCar to replace the injured David Malukas, posted a message to his own social media account calling on fans to consider their actions.
"I’m sad I received so much hate and death threats in the last 24 hours for such a small incident in the Detroit GP," the Frenchman wrote.
"I hope people can understand that we are all humans and we can make mistakes. But it’s not normal to abuse people online.
"Please be kind to each other."
It follows IndyCar releasing its own statement in 2023 calling out "disrespectful and inappropriate online abuse" following the Long Beach event, when Canapino's then team-mate Callum Ilott revealed he had been subjected to death threats from Argentinian fans.
