Absolutely. Those uncomfortable feelings and shame aren't a...

Absolutely.
Those uncomfortable feelings and shame aren't a mental illness. When you f-ed over your mate, you should feel horrible and uncomfortable.
It's a joke that they can trot that out as it trivialises depression, anxiety and mental illness. It wasn't a problem when no one knew about it.

Cheaters are scum. If you can do it you should own it. Also saying you have a mental illness casue you can't hack the consequences of your own decisions, think about how do you think your mate feels