The reason behind his remark was a 2014 incident where he wanted his fiancée to meet Rihanna as the two were in the same restaurant. He sent a request to Rihanna an she declined stating there was too many paparazzi outside.
Sheen went on Twitter, back in 2014, to vent about the incident:
oh and [Rihanna], Halloween isn’t for a while. but good on you for testing out your costume in public. it’s close; a more muted pink might be the answer, as in: none
See ya on the way down (we always do) and actually, it was a pleasure NOT meeting you. Clearly we have NOTHING in common when it comes to respect for those who’ve gone before you. I’m guessing you needed those precious 84 seconds to situate that bad wig before you left the restaurant.