I understand this position, but I still would say that it's muddying the semantic waters a bit. If you had "prejudice plus power" against someone in the LGBTQ community, would that also be called racism?

In general, I think the most common interpretation of racism would be "prejudice w.r.t. race" rather than "prejudice plus power". I would suggest that perhaps oppression is a more appropriate word to use for "prejudice plus power".