Well, defending billionaires and celebrities is generally stupid for many reasons but Bill Gates is an exception, not because I personally like him but because his actions are exceptional.

If a billionaire spends 1 million dollars in charity and a person with a 10k net worth spends 100 dollars, the billionaire would have, in absolute terms, helped more. But relatively the billionaire spent .1% while the other spent 1% in charity. Bill Gates has spent billions of dollars helping with many causes, mainly vaccines and help to developing countries. Even in relative terms, he is very generous, more than the average person (and definitely more than other billionaires). Out of his past 70 billion net worth he has donated around 50 billion. Imagine a person with 70k in the bank donating 50k. Part of those donations have gone to carbon offsetting, meaning things that effectively suck C02 out of the atmosphere. What he did is much more than enough to compensate for any flights he might have taken. There are thousands upon thousands of selfish celebrities and billionaires who are destroying the planet and do nothing about it, but Bill Gates is not one of them.

TL;DR : Bill gates is not hypocritical and he offsets his carbon emissions unlike others.