I think what's most beneficial is a healthy balance between loving support and setting firm boundaries.
We all know that our children are little scientists by nature - everything they learn is by trial and error. When it comes to tantrums/ naughtiness/ issues of discipline, they are again being scientists - they're trying what works and they will learn from our response. We can choose to either teach them to manage their behaviour or pacify them. If it's the latter, how can they learn what is socially acceptable? Surely the age at which they should learn this from us is the age at which they start behaving in ways that are not socially acceptable, right? If your child learned to walk in a way that was going to damage his/her spine (okay, silly example but stay with me) when would you correct them? Before or after they've established their way of walking?
When my DS throws tantrums I find that it's crucial to stop and observe what's going on in order to work out why he's so upset. For instance it's currently either teething/ wanting what he wants NOW/ something currently unfathomable! Once I know the cause of the tantrum I'm then in a position to work out the best way to deal with it - a one size fits all policy is simply not the ideal here. I think it's important (sometimes, but not always) to acknowledge his feelings when I can get a word in edgeways ('I know you're upset because you dropped your car...') - by this he learns to identify his own feelings.
After that my responsibility is to help him to learn from that tantrum - e.g. - 'you keep on dropping the car deliberately (to test me). I won't give it to you any more, you have to pick it up yourself' (yes, this level of complexity works with an 18-month old!). Other times I might pick him up, cuddle him close and speak softly into his ear, telling him jokes or singing or doing whatever I know will help him to calm down. The important thing here is that having observed the situation I'm in the ideal position to decide which card to play for the best outcome.
If we don't set boundaries early on (and they're not the only ones who need the boundaries, we do too - we also need practice setting them as it's bloody hard to do!) then it becomes much, much harder later. It also becomes more confusing for the child, because by that point they've learned what we apparently think is okay behaviour, then all of a sudden, months later we're saying it's not okay any more. It may make sense to us to delay discipline until they're older, but from the child's perspective it's inconsistent and confusing.