I doubt very much that greasing the rails will do much to prevent wear over a properly oiled gun. That said, it is equally unlikely that it will hurt anything and may benefit in some cases. In short, no need for either you or your friend to get militant about it. Do what works for you.
Just do your thing and let him do his. Next time just call him a moron.
I use Rem Oil, Grease and White lithium grease and mixtures there of on all of my firearms.
When you combine grease with oil you can usually find the perfect viscosity of lubricant your firearm needs in any particular area.
I have seen firearms that have been shot a bunch from people that do not lube their guns properly and then mine; that get shot all the time and I use grease.
My slides are not jingle jangling around and loose as a goose, still factory tight.
There are reasons lubricants like engine oils, grease, and gear oils are made. That is because every need is different. Some parts rotate, slide, cam etc. No lubricant is one size fits all.
Sig Sauer as I recall recommends greasing the slide grooves. Glock also send their pistols with a tad of anti-seize type of grease for aiding of break in.
I basically run dry. I use rem oil and then wipe the majority of it off with a clean, dry rag. I've never had any issues or noticed any excessive wear or failures. My ...
I switched to grease on the slides of my pistols and the bolts of my rifles and it is great. Wont stop using it. I have never had it gum up or stop anything from functioning.
I use hi temp synthetic grease with ptfe in it. It is a thinner grease usually used in high speed bearings. (A slide and bolt are highspeed was my thinking)
reducing friction is the idea behind keeping things lubed and keeping the frame/slide/barrel locking up as tight as the day you bought it
anywhere you would expect high amounts of friction, you'd want a thin layer of (insert your favorite chemical compound here). on semi-auto pistols, you're pretty much looking where the slide and frame ride together, where the top inside face of the frame rides the front of the chamber, and in the case of 1911's, around where the barrel and muzzle rub the bushing. everything else should get a good wipedown with said compound to prevent moisture/rust.
personally, i use shooter's choice fp-10 on all my stainless parts, mobil 1 synthetic on parkerized/blued parts, and remoil elsewhere. i have no scientific reasoning why i use these the way i do, i just prefer the way they work and make the parts look.
not to say using anti-seize isn't an acceptable lubricant, but the only anti-seize i've ever used (for cars) is copper and aluminum powder in a suspended "gel". mostly used when you have two types of different metal contacting eachother under high stress and temperatures (like buttering the back of an aluminum alloy rim where it touches the cast iron brake rotors) or on threads also under high temps (lug nuts or spark plugs). i would think anti-seize would work more like lapping compound than a lubricant when it is put on a moving part, but perhaps i'm missing some understanding or definition of anti-seize
I love my Shooters Choice grease.....can't beat the fact that it comes in a small sereng with a small applicator tip.......um word to the wize though......keep it off the sear......funny things can happen!!!!!!
m1 garand book recomends grease... That being said, i always lube with some tetra. keeps the lube where you put it...light coat of oil for rust prevention.
Lubriplate. All firearms including the AR. In the appropriate places and in the appropriate amount. Never in the winter. Refer to the Chosin Reservoir..
For all you Glock guys, did you notice the copper colored grease on the left rear when you got it out of the box? A little dab of lubriplate replenishes the factory grease.
There are plenty of modern lubes that work well too. I have grease that was provided by Uncle Sugar 40 years ago that I am still using and still have not got down to the bottom of the can.