If we don't Obey then we will be punished, that's the rule. So practically we don't have choices, We are not Free to Love or even to Hate but only to Fear. Accordingly, we must obey and live by Fear !

The previous conclusion is a perfect example for how a presumed question can be misleading!

As through our humanistic experience Living-by-Fear was the main principle that ruined whole societies for complete dark ages.

In my opinion, fear is an external factor with a temporally & limited effect that creates weak & unhappy entities lives by external dependencies .. which may act as external source of happiness!!

This external sources gradually start to feel authority and power over you and may at some point abuse it to harm you.

So if you started the debate with a question that assumes we were created in the first place to Obey followed by the punishment theory; what do you expect more than the Slavery as a conclusion!

Herein I am arguing that Obedience is a result rather than a goal!!
Where Love is the real goal not just a mean!..

In all religions and ideologies, Adam existed in first place for Building, not only with it's materialistic mean but also building Adam himself from a savage creature to the perfect one.

So the main point here is not Obey, but Love! because Love is a the only value that can build relationships between humans for collective work (Building) . Other values can also serve the same goal but up to limit. Hating a common enemy for example can lead to collective work but after this common enemy vanishes, hate will burn what was built. Another example is the Knowledge value! which also can build a lot but it always misuse what it was built. i.e. Nazi & Soviet regimes

Love as a core value of any ongoing civilization got physics and preconditions. For example, Love is a self corrective value that need Knowledge to protect it from haters. As a premature Love is a deadly naivety. Also Freedom as the only environment for Love to flourish.  I mean If you said once "I love" that inclose the ability to say "I hate" too, and if you are not able to say "I hate" then your love is fake and you are in captivity. He who is not Free to say "I Hate" how can he say "I love" !? 

If you choose to Obey by Love on a Freewill and a clear Knowledge about who, why and how to Obey then you are definitely more than a slave closer to a Son! A Unity relationship governed by the authority of Love not Fear unlike Slavery Relationship.

In the end, Must we Obey by Fear or by Love ? It is a personal choice so I can't suggest an answer. However, I will rephrase the question to Must we build by Fear or by Love ? and as a personal advice, don't ever be afraid, someone is going to abuse it.