I don't think its poor parenting, as long as the parents in question teach their children that it's "their" beliefs and give them the freedom to ask questions and decide for themselves. Unfortunately, its often not the case.
That being said, my kids are being raised with no religion yet I encourage them to look into things for themselves and have discussed a wide variety of beliefs with them (when they ask questions). I tell them it doesn't matter what mommy believes or anyone else, just what they believe. My nine year old is a borderline atheist, from her own observations. My seven year old believes in reincarnation in the same form as the native indians. I respect my children, so obviously I am going to respect their beliefs even at their tender ages.Why would I ever tell them, you are wrong, this is what you should think? To give them a moral compass? They dont' need religion for that, whatsoever.
These belief systems will no doubt change as they age and grow, but for me, I don't think its a negative to raise them religionless. What I do instill in them is belief in themselves, good treatment of others, morals without religious burden of guilt attached. Teaching them principals of humanitarianism and self-growth are the highest paramounts a parent can have IMO.
If a parent who has a faith choses to raise their child in it, with the mindset that they are passing on what they believe without dictating it is what the child is to believe, I have no problem with it. It's when a child is made to feel guilty or is chastised for expressing an opposing opinion or an original thought, that it becomes an issue in my eyes.