I don't think anyone is talking about ridding ourselves of IT. The guy is a special kind of weapon, certainly a keeper. Honestly, I love watching him.
All some are saying is the playoffs in the NBA is a different game. The physicality of the game really picks-up, and the refs more struggle to control it. Small bumps are more excepted, where during the season they were called as shooting fouls.
You have several 7 game series being played, where coaching staffs begin examining opposing rosters under a microscope. Advantages are planned for, as a prepared point of attack. Where in regular season they're more casually and simply mentioned.
If you don't think a 5-9 inch point guard, having to defend a top caliber 6-4 guard, for 35 minutes a game, isn't a disadvantage, (and 7-8" disadvantage)...you're kidding yourself. This 5-9 inch point guard needs to perform on offense at an extremely high level every game. Easier said than done.
Examine the past few years the Celtics got into the playoffs, and how IT was not the factor he was during the regular season. They planned for his defense, and planned just how he would be taken advantage of.
In a perfect world, A (fill in the blank with an NBA PG you like) starting, a player with a more balanced all-around game, with an IT backing him up, would give the Celtics a better chance of winning a playoff series, and a better chance of winning a championship.