"Blow that" or in this case "blow RH" here means the object of the phrase is not wanted. It is a reasonably polite way of putting some emphasis on saying "that's not for me." A more aggressively emphatic idiom could be "fuck that" or "fuck RH".
If you heard me actually speak it, instead of type it would probably make sense! I should probably lay off the idia and fall into line with generic en_*.
Bugger that!
