Not to be argumentative (as I sit here and argue with you

) but lactose is sugar. It's not refined or added, but neither is fructose (from fruit).
JMO, YMMV, I'm not a doctor, I don't play one on TV, I don't even like them....
edit
When you buy bacteria it will say on the bottle something like "1billion microorganisms per X at time of manufacture guaranteed". I have no idea how much is in any particular yogurt or how to decide whether it's being cancelled out, so to speak, by the sugar content.