Believe it or not, learning to lie is a milestone for autistic children; it's a social and survival skill. People are so used to dishonesty that they don't recognize that casual lies permeates our lives. From our earliest years, we are taught to always tell the truth. Here's the tricky part: being honest is a black and white rule, yet we live in a grey world. In reality, there are many shades of grey. Neurotypical children seem to have a natural grasp of when to bend and twist the truth. Sometimes it's more socially sensible to outright lie. If you ask an autistic child a question, you'll get an honest answer. A really honest answer.
Tact is sugar coating the truth or blurring the motive behind a statement. I used to consider any form of deception as wrong; now I understand that right intentions are more important than being right. My need for correctness clashes with making nice. The same way that there are rude neurotypcials, there are rude aspies. That being said, not understanding how or why to lie is a trait of Aspergers. For the most part, autistics do want to be polite and respectful although they may not always come across that way. My advice is to learn diplomacy; it goes a long way.
People unconsciously want appeasement, not the truth. Society relies on certain accepted and expected forms of denial. Despite my brutal honesty and straightforwardness, I've always been very sensitive to other people's feelings. I've been made fun of enough in my life to know that I don't want to make someone else feel that way. As much as I've treaded carefully in my verbal exchanges, I struggle with impulse control because my brain operates faster than my artificially constructed filter which results in blurting things out accidentally. There are things I've said that I deeply regret. In my grade 11 English class a thought popped into my head that may have been appropriate to share with my friends in a certain context but certainly not in front of a class. I'm not sure how but my mouth sped right past my filter and I said my thought out loud. Very loud. The boy who was presenting up front stopped talking and I froze. My teacher blushed and the entire classroom gasped in shock. The silence that followed was deafening. If looks could kill... I kept a stoic expression but I wanted to disappear. I'm pretty sure it was after that slip up that people started calling me crazy. I can completely empathize with someone who has Tourette's, which by the way overlaps with autism. There has to be a connection there somewhere.
Tourette's = involuntary tics + vocalisations
Autism = stimming (some have tics) + low impulse control for blurting out thoughts/ feelings
When you meet an autistic person who's never learned to filter themselves, you'll understand why it can be problematic. Even though I have a pretty good grasp of social etiquette and convention, I still stumble at times. Sometimes I stumble so hard that I land with my foot in my mouth. It's easier to forgive myself when I remember that it's not exactly my fault. I just need a discreet shush or a gentle nudge to be honest to a halt.