You may want to ground your advocacy in real-world data. This is a widely discussed topic. You might want to start with
http://www.theatlantic.com/business/archive/2011/07/the-case... .
The salaries of public sector workers are public, as are the CEO and other parts of upper management in public companies. Everyone's salary is some countries are available to the public.
Quoting from that Atlantic article:
> The worse the individuals' pay was relative to the median, the worse their satisfaction. Those at or above the median, however, experienced no change in job satisfaction or job search intention.
> These economists conclude that pay transparency just makes workers who are on the low-end of the pay scale feel worse about their jobs, so it accomplishes little. Linda Barrington notes, however, that this contention misses a benefit of being unsatisfied: the likelihood of moving on .... to another job, which would match that improved performance with better pay
Regarding the second, backchannels, again we can look to real-world examples to show how difficult or delayed those backchannels might be. Consider Lilly Ledbetter, who was hired as a supervisor in 1979. It wasn't until (quoting from http://content.time.com/time/nation/article/0,8599,1874954,0... )
> Shortly before she was due to retire in 1998, an anonymous co-worker slipped a note into her mailbox at work comparing her pay against that of three other male counterparts. Ledbetter was making $3,727 per month, while men doing the same job were paid $4,286 to $5,236 per month.
Quoting now from http://www.nwlc.org/resource/lilly-ledbetter-fair-pay-act-0 (emphasis mine):
> Her co-workers bragged about their overtime pay, but Goodyear did not allow its employees to discuss their pay
She filed an EEOC complaint, which the Supreme Court said wasn't allowed under the law because it the discriminatory acts of the past decades were older than the statutory 180 days for filing an EEOC complaint. The result was the Lilly Ledbetter Fair Pay Act of 2009, which resets the clock after each paycheck made from the result of a discriminatory act.
Here's another article, http://www.financialsamurai.com/never-tell-anyone-how-much-m... , which says, basically, never tell anyone else your salary.
Since it's easy to show existing cases where people don't talk about their salaries though back channels, your belief that "people already talk about salary" may be true for some, but surely is not universally true.
Plus, how many of those people are not telling the full truth?