Absolutely silly to call Chappelli racist. He's one of those old school outspoken pundits like himself, Boycott, etc., who call it as they see it without political correctness and they are equally critical of their own teams if they're playing bad as Boycott is often.
Chappell's comments did not come after a particular tour, but as a culmination of a series of tours where Pakistan has failed to even draw a single test in Australia since the mid 90s. Very few teams win tests in Australia, but a 100% losing record for 20+ years is just unacceptable for any team, not least a team like Pakistan with its history. I'm betting Chappell's comments, as harsh as they were, were more a lament and from a place of concern on Pakistan's current state, as he was used to playing strong Pakistan sides during his time, rather than to denigrate or insult it as a country. Sometimes a kick in the back from the well wishers would serve better than fake kind words that don't force a change in results.