This is patently untrue. Provide some data or get out of here. Squats are universally accepted as one of the best natural movements of the body to train.
It all depends on your objective and goals. As with everything moderation is key. A balanced program of squats, deads, pushing exercise (chest/pecs) and a pulling (back/delts) is best for oevrall muscle, bone and tendon health. Whether you do this via free weights, body weight, or machines is really not material.
Rippetoe style heavy free-weight squats, squats and more squats is not the be all and end all of resistance training. Personally, I got into heavy strength training with Rippetoe's books and videos - and, IMHO, he did a great service by educating people about the benefits of heavy (free weight) strength training using a very very simple ('KISS') type program (at a time when the focus was on machines and overly complicated routines). His routines are great for beginners - especially very young ones - hence why they are copied and 're-mixed' so much (like Stronglifts 5x5 and countless variations thereof).
And I would really not suggest heavy squats for improving grip strength - that would be a very inefficient way to train your hand grip.
http://www.bodyrecomposition.com/muscle-gain/squat-versus-le...
http://www.thedreamlounge.net/barbell-squat-worst-exercise/
http://ericcressey.com/newsletter91html
https://criticalmas.com/2012/06/i-no-longer-give-a-squat-abo...
http://community.myprotein.com/off-topic/28225-mark-rippetoe...
https://forums.t-nation.com/t/rippetoe-ripped-apart/191700/7
https://www.bodybuilding.com/images/2016/may/what-all-squate...
i agree that squats CAN be good for you, but I am stating that the risks outweigh the benefits. Just one bad form squat in your entire life, and you can permanently damage your knees or back. there are much safer exercises that train the same muscles.
as far as provide some data or get out of here, unfortunately I do not know of any good data source on weight lifting injuries and hazard rates.
The best I have is baseball, the toll being in the squatting position takes on players knees is, to use some of the language you have used, 'universally accepted'.