Would society be better if we didn't feel guilty about sinning?

Yeah, probably. Religion is a major guilt trap in many ways.

Guilt is a gift that draws us away from sinful behaviors that cause us and others suffering and sorrow, which is precisely why God has forbidden them. Having casual sex doesn't hurt anyone??? Millions of cases of venereal diseases; women treated like objects that can be used and discarded; thousands of innocent children brutally slaughtered during the first nine months of their lives. Shall I go on?

Guild is the mind understanding that one's thought or actions were wrong or violates the 'morality' of one's society. Sinning is assuming that they offended one of the many gods.

No, it would not.  It would be even worse than it is now.  If we stifle our conscience, we're apt to do anything we please.

'Sin' is a imaginary concept that the people who inferred the existence of a 'perfect god' who would only be capable of 'perfect creation' used to rectify the existence of an objectively 'imperfect' world and human race.

No, God gave us all a conscience so that we would not sin.  If you did not have a conscience, you would not know what was right and what was wrong. That small, quiet inner voice helps us to get a grip and not to steal, kill, lie, rape, etc., or do bad things in life when we are tempted to do so.

That inner voice speaks to us, and we come to our senses and ask God to help us not to do what we were being tempted to do.

Conscience is good for mankind.  Those who have switched off their consciences, end up murdering people, raping people, and  in court, because they have switched off their voice of conscience, they laugh and are not repentant for their murders.  That's what the Lord says will happen in the final days, "They will not repent of their murders or of their fornications or thefts etc.," and that's why because they have hardened their conscience, so that it doesn't bother them anymore. (Revelation 9:20 & 21 and 16:11)

Can you imagine what society would be like if everyone did that?  There would be no restraint whatsoever.  Life would be mayhem and that's exactly how it's going to become in this world, once God takes Christians and the Holy Spirit away.  Then folks will live in that dreadful world they themselves have created, but we Christians will be out of it all, in heaven in comfort with our Saviour.

A scientist wrote about that, relating an event he witnessed. "A family were standing in the large kitchen of their home talking to friends while their 3 year old daughter pushed her doll’s pram to and fro with some vigour. In doing so, she ran the pram into her father’s leg, inflicting (as I remember) a degree of pain. The child’s older sister immediately issued a stern rebuke: ‘Alison, say sorry to daddy!’ The younger child continued her perambulations without response but we could see her mind was working overtime. ‘Say sorry to daddy!’ came the repeated command. No reply. A further interval elapsed and the older sister’s voice rang out again: ‘Say sorry!’ There was a prolonged pause and then the worried frown on the toddler’s face was suddenly replaced by a seraphic smile: ‘Me can’t talk,’ she said.

The adults dissolved in laughter but I have never forgotten the incident because its implications are really quite profound, illuminating the whole question of human morality. Clearly, Alison knew she had done ‘wrong’ in hurting her father. Her stubborn refusal to admit guilt is evidence enough of that. If she had no sense of right and wrong she would have experienced no moral dilemma.

We would, of course, explain the episode away. It wasn’t that the child had some innate moral awareness, we might say, but that her sense of guilt was a conditioned reflex. She recognized her sister’s tone of voice and knew from past experience that it meant trouble. No doubt, children do have conditioned reflexes, but the appropriate reflex in my story would have been one of two things – either a simple denial of responsibility (‘it wasn’t me, it was my doll’) or a quick apology (knowing that an apology defuses such situations). It was the devious guilt-reaction that revealed the toddler’s moral awareness – her silent inward struggle spoke volumes. She knew she was guilty and should apologize, but exercised considerable ingenuity to bypass conscience and evade moral responsibility. And you can’t evade what you don’t have.

Such behaviour is typically and uniquely human. We can only experience such problems if we have a genuine moral sense in the first place. If, at that moment, the family’s pet dog had walked into the kitchen leaving muddy paw-prints, it too might have been scolded. It might have cringed and put its tail between its legs, recognizing disapproval in its master’s voice. But this would be a genuine conditioned reflex, a response to an external signal. There would be no corresponding inner awareness of wrongdoing – otherwise, next  time, it would have wiped its feet on the doormat.”

So the answer to your Q is that even toddlers have a wired-in conscience that prompts them when they do even slight things that are 'wrong', as opposed to animals like dogs only feeling worried about punishment or trying to please their masters. Whether we call wrong-doing ‘sin’ or just a mistake, a guilty conscience helps prevent indifference to that, and all society benefits.

Who Made God? - Searching for a theory of everything - Edgar Andrews - pages 263-6 (EP books 2009)

Yes, just imagine all the people living for the day. 

I don't think so. We might go into a slippery slope. We might go in a downward trend if we start believing that sin is ok to do. Life is better if we start making ourselves stronger into not sinning.

Guilt is a corrective emotion to steer us away from destructive behaviors.

All sins hurt the sinner, and many times innocent others. 

So no.