Thanks for sharing your side of this story. But surely there is a difference between a red elephant emoji symbolizing the GOP and an emoji that is meant to imply something more—something insidious?
Advertising channels have the right to determine what is acceptable for their platform and to reject ads if they so choose. If the Trump campaign had requested a custom emoji of a less incendiary hashtag, I doubt things would have unfolded this way.
Having said that, I do agree that all political parties should be treated fairly, so if there are any examples of Twitter granting custom emojis to similarly incendiary hashtags (like if Clinton had purchased a custom emoji that alluded to Trump’s sexual assault allegations), I would be very interested in seeing them.