"There are two things you can never do: spend someone's money and raise their kids."
I say this a lot, because in our day-to-day lives, I see the gamut of child raising philosophies and tactics among my family, friends, and people on the street. It's difficult, because as a parent myself, I look at my four amazing kids and think, "Yeah, I did OK." This thought progresses to, "Everyone should do it like I have," which is what scurries through my mind just before one of my children do something that leaves me banging my head against the nearest wall.
I don't believe child rearing is a science. Raising my kids has been much more attune to an artistic expression. And, just like art, there are a wide variety of ways to do it, appreciate it, and judge its "success." No one parent does it the same - not even in a couple working together for the well being of their kids always see eye-to-eye. The key to accepting other parenting styles is to understand that differences don't have to be divisive. Differences can be enlightening. And, like art, since there are so many variations, just because some one does something different doesn't make your way - or their way - "wrong."
First off, understand that, if someone chooses a different child rearing method than you, it's not a condemnation against your choices. Or put another way, just because someone else does or doesn't do a thing should have no bearing on the choices you make for your own kids. If you can accept that, and make decisions for your children based on their needs, personalities, and your own family dynamic, you'll remove much of the self-imposed pressure to compare and contrast the variety of parenting styles with your own. You can be freer to understand that, like art, it's not "good" or "bad," but different. Take a breathe, and focus on what your kids need, not on what other people are doing or not doing.
Next, recognize that every child is a unique individual. Considering that, you have to understand that a technique or method used for raising one kid just won't work across the board. I've seen that in my own four offspring. While my oldest was the textbook first born, perfectionist rule-follower, my second born was the "you can't hurt me" and constant "why?" child. So, while I could leave the oldest quietly watching a video while I did housework, the second needed something to keep her busy, or chaos would ensue. When you look at another parent engaging their child, keep this very important fact at the forefront of your thinking. The child he or she is dealing with is not like your child. So, what you think is right or wrong may not even work with this wily little one.
Cultural differences play a huge role in parenting styles as well. Before sitting in judgment on someone else's child rearing, think: Did they come from a different culture, where different character traits are emphasized in children? Does their style reflect a specific cultural bent or tradition that we might misunderstand?
The wide variety of parenting styles also gives each of us an opportunity to learn from everyone we encounter. Most of us fall into the patterns we are most familiar with. As many times as we vow to not be like our own parents, instinct takes over and unless we make a conscious effort, we tend to raise our kids the way we were raised. A wise parent takes the good they want to emulate and incorporates those things into their own parenting practices, and lets the other stuff slip away. When dealing with someone who's parenting style differs from your own, the same principles apply. Most people do something that might be beneficial in our relationship with our children. Find those things, and focus on them as you attempt to appreciate their methods.
Remember that your background, training and experience is different that the other parent. We are a sum of what we have experienced and learned before, multiplied by the potential of what we can be tomorrow. In this equation, we all have different "numbers" we're working with. Maybe you've read a book that helped you raise your child a certain way that meshed perfectly with their personality. Great! Perhaps, if you have relationship with the parent and can do so in a non-judgmental way, you can share the book with them. Otherwise, grant the parent in question some grace, and understand we all come from a different skill set.
No two people are identical in every way. Differences are what add diversity and fun to our lives as members of the human race. In the area of parenting, where emotional investments run high, it's easy to let these differences divide and separate us. Instead, we need to focus on how these differences add to the variety that is humanity. The next generation we are raising will only benefit from our patience and willingness to understand and accept one another.