Obviously a problem for some people and, much as I've enjoyed Apu, I am in sympathy with them. Apu is perhaps a dated stereotyped caricature - though we mustn't forget that every character in the Simpsons is exactly that too. Perhaps I wouldn't find him funny if my ethnic origins were from the Indian subcontinent, yet I don't find him funny because of that but because of the exaggerated character, a feature common to all in the series. Nobody is really exactly like that but we see bits that we recognise. Like Alf Garnett.
I just checked and see that new episodes are going to be made up until 2019. Perhaps Matt Groening could tone Apu down, make him more of an all-round person and introduce an Asian-American family. Certainly the opinions of those offended by the current Apu need to be considered sensitively, it's not difficult to see this from a different point of view.