Is yogurt a cure for diarrhea?

Not really. The resaoning behind that is that ogurt contains probiotics. The dairy part of the yogurt though can cause diarrhea in some people or aggravate it in others. Just take probiotics and skip the yogurt...As it is the probiotics that help.
No. May help recover from an infectious or antibiotic associated diarrhea though. Most yohgurts have lots of artificial sweeteners and flavorings which make them of little benefit. Some have actually been chastized by the fda for making unsubstantited claims.