He is right and wrong at the same time.
The stock LCA's are U shaped and not boxed so that they can twist when your suspension articulates. When WJ LCA's they are boxed and have hard rubber bushings on both ends, so as your suspension articulates it will stress the mounts on both ends. Eventually, the mounts on your axle side will tear off of the axle.
That said, with 1.75" lift and 31's, you probably aren't going to be articulating it a lot and it would be fine for a while.
The stock LCA's are also known to literally fold like a taco.
When the LCA mount goes, it looks something like this, and then tears off totally.
If you can find a local member with a welder, you can weld mini skids onto the LCA mounts fairly cheap that will help that. Its a simple task, and most members will help you with it for a 6 pack of fine beer.
I suggest the ones from JKS Manufacturing.
http://jksmfg.com/i-9056868-fab-cherokee-xj-comanche-mj-1984-2001-miniskid.html
As far as WJ LCA's go.. they are better than running the stock ones, but really you'd be best off to save your penny's and buy some Rubicon Express or similar ones that are intended for the way we use our vehicles. Better quality control arms will have a 'flex joint' of some type on one end or both, and allow the arms to twist without stressing anything.
I'd look at replacing the upper arms as well, they too have a habit of folding under duress.
http://www.amazon.com/Rubicon-Expre...ywords=jeep+lower+control+arm+rubicon+express
http://www.amazon.com/Rubicon-Expre...ywords=jeep+upper+control+arm+rubicon+express