If you read the examples I gave above, they're not vague. Dog-whistles are more for plausible deniability than subtlety, and it's because (shocker) white supremacy is frowned upon. If you think liking white people requires openly advocating white supremacy, and anything else is an implicit statement that you don't like white people, then that really says more about you than anything else.

They try to promote their non-white figures because their agenda and campaigning for the most part is so overwhelmingly targeted toward white voters that they have horrible reach into other demographics.

This is like the Black Lives Matter vs All Lives Matter debacle. Minorities are brought into the spotlight because there are systems and large groups of people actively working against them. Meanwhile, you don't need to "promote" whiteness, because that's seen as the default in America.