I also think there is nothing wrong with seeing a therapist. Or seeing a nutritionist. Or seeing a personal trainer. Or for that matter seeing any professional to help you resolve an issue you are struggling with.
But why would one see a therapist if nothing is wrong? Note I am not saying wrong with them, just wrong. A person goes to a therapist to fix some kind of problem, I think. I go to see a nutritionist to fine tune my diet for example, and I have a six pack. Nothing wrong with me, but there is something wrong with my diet obviously cause I wound up pretty ill by following it.
So I think (also because I am learning as I go, as in my other thread) that giving the advice to see such a professional can be a very risky proposition. You really have to know how the other person will react and know them well. Just offering someone to see a therapist without that background can be very insulting. Even without the stigma.
Well, but offering to critique their diet can also be insulting. I don't think it's any less personal or any less sensitive for many people, so you have to tread carefully.
And yeah, mental conditions are "something wrong" in the same sense that a broken leg or the flu is "something wrong." The stigma is what bothers me--there's this idea out there that a mental illness means you're "weak" or that it reflects badly on your character; and there's another idea that mental illnesses aren't real and that you can just make depression or PTSD go away with a "chin up!"

When, really, they're a condition just the same as an injury or a virus, and there is treatment for them, and it doesn't make you a bad person if you have one any more than you're a bad person if you break your leg.
I agree that it can be very risky to suggest any kind of professional help (doctor, therapist, nutritionist, whatever) and that you have to know your audience. And you have to be coming from a place of real caring and not flippancy. It's rude and dismissive to go around, for example (and I'm not saying you do this personally; this is a general "you") hectoring every smoker or fat person you see about how they need to quit/diet. But if you are close to someone, and you think there might be a specific issue they haven't thought of yet, it can be different.
Another example from my real life: There is a rare chromosomal condition that, by dumb chance, I had two friends who had it. So while I'm not a doctor, I spent more time being around the condition and talking about the condition than most laypeople ever do. A third friend confided in me some symptoms she'd been experiencing--some for many years--and that she and her doctor were both stumped. I told her, "I have an off-the-wall thought, but I'll keep my mouth shut if you prefer." She said go ahead and tell her, so I told her that she might want to get checked for this condition next time she was at the doctor, because she had symptoms x, y, and z that can result from that. (IIRC, she ended up deciding she probably did have it but didn't want to go through the testing.)