The "he's a racist" narrative isn't going to work, and there's no litmus test for determining who is a racist and who isn't, beyond common sense which doesn't likely apply to Trump.
It's merely a talking point which has been in use since the very beginning, and most likely doesn't relate to actual policy or actions, but rather tangential things. Pointing out that he has racists who support him, for example, is a strategy that has been in use long before Trump ran for office (similar talking points were used against Ron Paul, for example).
If you keep up with this, you'll eventually have to try to argue that more than half of Americans are racists, fascists, or Nazis due to having voted for him, and that narrative simply won't fly due to being one of the most common and uneducated talking points used by opposition. It's proven ineffective in two elections, so coming up with something more original is likely in order.