At the risk of sounding snarky or disrespectful, I can't fail to notice how often people suffering from depression become all passionate and fiery when discussing the cause of (their) depression.
The thing that gets me (and others) worked up is when people make sweeping generalisations regarding the causes and treatments of depression. No one likes being painted with a broad-brush, but it adds insult to injury when something that has caused me so much suffering is dismissed as trivial and easy to solve. I've spent more than a decade trying to treat my condition. It's not as simple or easy as most people think.
I guess it's also an issue of semantics: 'depression' is a very broad term that gets narrowed down in our minds, based on our own personal experiences. When I hear it, I tend to think of the more serious kind because that's what I've lived through: not leaving my house for two weeks, not showering, eating or sleeping for three days etc... I can understand why some others might think of it more like 'that time my goldfish died and I was sad': this is the fortunate extent of their experience of low moods.
Or maybe I just envy those without brain cooties...