Gregan's pregnant wife, Melissa, and young son were threatened by a group of people after the 2-0 defeat by Leicester last Saturday.
He told BBC Radio Leeds: "I've had about 600 e-mails and cards, several bunches of flowers for my wife and cuddly toys for the little lad.
"It's just reaffirmed what I thought about this club and the fans. It's a great place, and where I want to be."
Meanwhile, Leeds have launched an investigation into the incident.
"The matter is being investigated, and we think we know who is responsible,' said club spokesman Bill Morris.
"We are obviously 100% against anything like this and we take the matter very seriously. We are very upset and if we do find out who the culprits are they will get a hefty ban from the club, we cannot allow this to happen.
"It is important to remember 99.9% of true Leeds United fans are not like this," Morris told Leeds' official website.