Lying is acceptable but not always practical. For example, lying to your boss about union activities is praxis, but lying to your comrades can destroy solidarity if you are found out.
I think if you're a materialist you have to be pretty accepting of lies that don't directly harm anyone. If a lie doesn't directly harm anyone and it helps advance us towards a material improvement, how can a materialist not at least be fine with it?
The fundamental problem is that while you want to be as truthful with people as possible (for all sorts of reasons), people rarely make radical changes to their beliefs all at once. Most people come around one step at a time and will punch out if you push too much, too fast. It takes a determined effort to keep people moving in the right direction. So if you lie about something distant that would cause them to instantly, unthinkingly reject you, but you make progress with them on some more immediate subject, how is that not acceptable? The alternative -- complete truth that alienates the person you need to persuade -- doesn't get the job done, so it can't possibly be the right answer.
Agitation/propaganda is a form of lying, but it's an integral part of organizing for change. Now lying to subvert the needs of the workers and steal their surplus value, that's bad.
Based on a cursory google search, one study found that there were a few categories of lies ranked by "acceptability".
1.Saving others from minor hurt, shame and embarrassment. 2.Protecting yourself or another from punishment or disapproval for a minor failing or blunder which hurts nobody. 3.Making yourself appear better than you really are or to protect some gain, acquired some time ago, to which you were not really entitled. 4.Lies that could make others do something that would benefit you while, at the same time, harming themselves or causing themselves a loss. 5.Lies that hurts someone else so that you can gain.
However, each of these are relative. If the someone that you're "hurting" is a business owner exploiting his workers then most of these lie categories are probably okay. If they're towards your friend or a colleague or a stranger then maybe only the top 2 are okay.
https://www.tandfonline.com/doi/abs/10.1080/00224545.1983.9712018
most people are bad liars and most lies are hard to conceal
The most common lies are stuff like "I have plans that night, sorry." People pull stuff like that off all the time.
