Yeah, no kidding. 
You seem to be quite sarcastic and disingenuous about this, when there are established laws regarding intellectual property, as well as specific provisions such as the fair use doctrine for when you can use IP. It’s also worth noting that reviewers also get quite upset when flashlight companies steal their photos for commercial advertising, so it’s not exactly inconsistent, and even if it were legal doesn’t mean it’s necessarily ethical.
Quoting with citation is not legally or ethically equivalent to wholesale duplication of copyrighted material without attribution. Much of what exists today is reliant on intellectual property protections, otherwise there would be little incentive for it to be developed.
I'm dead serious.
I want to know where the line is so that I don't cross it in the future.
If you think you can enlighten me, go ahead.
(So far, you haven't enlightened me on the bold section.) 
LOL, BitChute only exists because no one else will host their trash.
Not sure why you can’t do the research yourself, like about DMCA, the Fair Use Doctrine, etc, but very well here’s a helpful reference:
https://ori.hhs.gov/education/products/roig_st_johns/Copyright%20Infringement.html
Here’s a textbook some law schools use as part of their curriculum if you think I’m just blowing hot air Amazon.com
Also, here’s a reference for if something has a permissive use license like Creative Commons About The Licenses - Creative Commons
I followed those links, and I'm not reading that.
If you cannot explain in plain words where the line is, that's fine.
For your information, and for the future, providing a bunch of links like that to a mountain of text is not helpful.
I'm looking for an answer that clear and concise.
I'm not looking for a bunch of legalese that's tough to comprehend and takes forever to read.
The links aren’t exactly complex legalese but since you’re demanding it to be spoon fed to you, I’ll baby it down for you:
Don’t take other’s photos without asking for permission first, many times people will allow you to use it if you give them credit, and it wouldn’t’ve been hard to credit those whose photos you stole.
Forget it.
You're just talking down to me and not answering my question. 
He did answer your questions though. You chose not to read it.
We'll have to agree to disagree.
I read his post.
I want to know Where is the line that one must not cross?
He did not answer that question in a clear and concise way, and now I don't want him to because he is being condescending.
As an adult, you can still ask, but you can’t expect everything to just be handed to you. But people are trying kindly and directly to hand you the answers here. You come back with “not good enough” to everyone so far.
If it’s hard for you to comprehend it from what’s been said or hard for you to search for information and answers on the internet, then remember this….something we teach to our children:
“If it’s not yours, don’t touch it.”
And call it a day.
Otherwise, some adult communication and interaction skills can work out the rest of it, usually without harm. I mean you basically deflected everything and called him a dick for being upset and confronting you (and yes, he was pretty flat and direct about it, wasn’t he…here and on reddit both, but possibly upset that you were posting it in several or many places for all he knew). And then you didn’t want to be called out in public and said you’d prefer it to be behind closed doors in a PM. Ok. But you didn’t even just say a simple, “hey, sorry man.” Do you see why at this point it’s not just the owner of the “property” that is upset, but several you’ve interacted with on both forums now?
As for myself, when I saw his post, I did sit up straight and was like, oh crap, I did the same thing basically…although I did credit him clearly and his watermarks were in the photos. And it wasn’t for my own gain, so to speak. I don’t think you gain anything from sharing about a light you’ve used, either, but the two situations were obviously perceived differently, y’know? But now, knowing how he feels about his work, and even though we’re sort of all one big flashlight family, if I feel the need to use any of his great photos in the future, I’ll ask him first, no problem.
It could be that after being in this forum for 12 years that he may have expectations that you would know something he thinks you should know, too (right or wrong…that’s just how people often work).
But give the man a simple apology and don’t do it backhanded like that, and everything will probably be fine. In the future, try not to do things that require apologies or backpedaling later. 
Hindsight is 20/20.
I had no clue that anyone would get upset over this.
I've already said that I will make it right.
I would apologize, but not to someone that is so completely rude to me.
The most rude thing I did to him was call him a name that he actually deserves.
I have since changed that word to "jerk", but of course that means the same thing.
The line is simple. Don’t be a dick. Stealing images without permission and then using them in your reviews without even crediting their sources, is a dick move. Next time, ask the source and give them their well deserved credit for putting in the work you don’t want to do.
I think I have the answer to my own question.
If you do a review, you must use either your own photos or the manufacturer's photos.
If you want to use someone else's photos, you must get their permission first.
If you just post something on a forum that isn't a review, then you don't need to get someone else's permission.
The line is between posting a review and posting something that is not a review.
I was hoping for a better description of what the line is that you must not cross, but I think I understand the concept now.
Respectfully, that's not a line, but I figured it out already so we can put this issue to rest.
Crossing a line means that there is something that is allowed, and something that isn't, and what separates those two things is the line.
Please continue the petty bickering. I find it most intriguing.
Is this a quote from a Star Trek episode or a coincidence?
Eh, I was close…
