On Lashon Hara, and the sources thereof

I subscribe to a number of daily emails regarding the laws of Lashon Hara (I'm sure you can tell from reading this blog what a wonderful impact it's had on my way of thinking and outlook! Be that as it may...).
I've become much more aware of conversations that may constitute or contain L"H, and I do, in fact, try to avoid talking about other people, at least if they can be identified. I try not to initiate conversations - even innocent ones - that may lead to inappropriate discussion. And to the extent that I can reasonably do so, I try to end inappropriate conversations quickly.
To me, it seems ironic that shul is a - maybe the - primary source of lashon hara.
There are two major ways this works:
First is the actual talking that goes on in shul. This includes during davening, laining, etc. Of course, most talking during davening is wrong, but certain types would clearly be more wrong. And this category also includes conversations after services, like at a kiddush, or just standing around waiting to go home.
The second way shul is a primary source of lashon hara is when it acts as the "cause" of it. "The rabbi's speech was much too long." "It always is." "I stopped listening; I couldn't follow it anymore." "Did you see (so and so) fell asleep as soon as the rabbi got up?" And, "the laining was terrible!" Or "the laining was pretty good - much better than he usually is!"
The responsibility for almost all of this is on the individual. Regardless of the validity of the point, it's just idle chatter and loshon hara.
But some of this is addressable and preventable by the shul! If (the vast majority of) congregants don't want a long drasha, let the rabbi give a shorter one (perhaps with a longer one after davening). Don't have bad ba'alei tefilla regularly (yes, "bad" is a subjective term, but there are some people who clearly should not daven with any frequency).
My bottom line: yes, people are going to (inappropriately) talk anyway, and they shouldn't, and that's each person's responsibility and problem.
But don't give them more fuel for the fire! To me, it seems like an obvious case of lifnei iver lo sitten michshol - don't put a stumbling block in front of a blind person.