Again.
Remember the birther thing? Where he accused the first Black president of not being legitimate?
There is no debate about this.
If you don't consider Trump racist, you are likely a racist yourself.
Believing a president was born in another country doesn't make someone racist. Maybe for some people it has something to do with racism, but the primary reason for believing in it is intense partisan loyalty and a desire for political delegitimation of the other side. Obama's complicated early life history makes an easy target for claims of hidden secrets.
I think there was also the issue of Obama's middle name being Hussein, and in 2008 Saddam Hussein was very recent memory.