I've come across quite a few angry people who have disabilitites, chronic conditions and live with ongoing pain.
And I can see how that can wear on you.
When I was in nearly constant back pain for 2 years I had no idea how much it had affected my personality until the chiropractor sorted it out, almost overnight - and I reverted to the Pain Free Me. What a difference.
So, to answer your question, I don't think that diabetes makes people into angry people. But I do think that the stress, strain and possible pain/distress etc will affect a lot of people who have diabetes. But probably no more than other longterm, physically challenging, possibly painful conditions.
And the people who bear the brunt of that are going to be the carers, partners, friends and relatives.