Obviously not everyone who has a reasonable amount of sugar gets fat or diabetes.

However, NO ONE has actually claimed that straw man. This culture of 'only drink things that have at least a hundred calories of refined sugar added' is a huge problem for weight gain and diabetes.

In your analogy, yo usay removing the pancreas causes type 1 diabetes. This is absolutely a cause. Yet on the other hand you seem to be arguing that since there are other causes besides high sugar diets that can also cause type 2 diabetes, you shouldn't say high sugar diets cause diabetes.

High sugar diets are a huge risk. Some people manage to get away with such a diet without diabetes (but likely get other issues with weight gain), and some people have the misfortune to get it anyway, but the fact remains a high sugar diet can result in diabetes, though arguments can be had about how direct/indirect the relationship is.