Of course they are going to boo. Zero contact up top, Kawhi landed on his foot. It is definitely a foul, but every home crowd in the league boos that call during a playoff game. The fans aren't exactly objective.
Look, I hate 90s style basketball, but everyone calling this play dirty needs to go watch some clips of Laimbeer for some proper perspective.
There is dirty like Zaza and then thug-a-nomics aka Laimbeer.