The blocked off doorway is a remnant from the expanded original Japanese edition of the game. In Japan the "e-reader" system may be used to earn extra content at this location by scanning cards with special "dot codes." In America the "e-reader" system is available, and you can scan cards, but pretty much all you can do with it is get information on Pokemon and items. A function that is only really helpful when you're looking for the location of one particular pokemon. I suppose they figured it was easier to program in a tree rather that program out a door.
Chat with our AI personalities
Talk to one of the people in Sootopolis City (can't remember which one... Maxie? Steven? Wallace?) and they will get the guy to move out of the way.
FLY to Fuchisa city and the house next to the pokecenter is the move deleter's house
The house that is downward of the Pokemon center in Canalave city
in BLACKTHORN city (the last house)
The move deleter's house is next to the fuchsia city Pokemon center.