The poll, commissioned by ARD, a public broadcaster with rights to Euro 2024 starting in Germany on June 14th, said that about one-fifth of those questioned said they wanted more white players in the national team.
On Saturday, national team player Joshua Kimmich called the poll racist and his coach agreed.
"Josh responded really well, with a very clear and thought-out statement," Nagelsmann told a press conference.
"I see this in exactly the same way. This question is insane."
Germany's team competing at the Euros has Black players, as well as players with Turkish background among others.
The broadcaster said a reporter working on an ARD documentary on football and diversity was repeatedly confronted with statements about the make-up of the team during the making of the documentary.
It said it commissioned the poll in order to have measurable facts on such statements.
"I was shocked that such questions are asked and people actually answer," Nagelsmann said.
"It is racist. I feel we need to wake up. Many people in Europe had to flee... searching for a safe country.
"In Germany we are living well and we tend to shut out these things. A football team can be a role model of how to unite different cultures, religious backgrounds and skin colour.
"It is good the way it is now. We play a Euro for everyone in the country and whoever plays top football is invited to be a national team member. I hope I never have to read such crap polls again."
Germany open the tournament with their Group A match against Scotland on June 14.