Hmm...if a person is going on a diet or trying to change their lifestyle to be more healthy then why buy, and bring into their home, cookies, ice cream, chips, and junk food? It's just to tempting ~ why torture yourself! If that stuff is easily available and accessible then chances are they will most likely eat it.
However, if it's not in their home and they can't find any "junk food" in their fridge, pantry and cabinets then they are more likely to stick to a healthy plan with healthy habits.

Don't torture yourself by having "junk" in your home and stay away from the people who encourage you to eat it. Instead, surround yourself with people who support you and encourage you to live and eat healthy.

I'm not a nutritionists nor a dietitian but I think it's probably okay to have a small serving of something sweet every now and then without having to feel guilty. To me, it's all about exercise and portion control. I pay attention to what's in people's grocery carts when I'm at the grocery store and very little of what I see would be considered healthy.  

If you want to eat junk food then have at it but don't come complaining to me afterwards that you're unhappy with your body and you're mad that you're gaining weight and you feel bloated and your clothes fit you tighter and blah, blah, blah.  
I will support those who are honestly trying but I won't support those who talk the talk but aren't willing to walk the walk. 
It's called COMMON SENSE.