Well, that was a joking statement on my part, but I suppose if we want to turn it into a srsbzns debate, we can do that too.
I did not see anything in your original statement that indicated it was meant as a joke, nor did it feel that way, so it seemed to me you went all defensive and serious about it, but that's fine.
1). There are no protagonists in 40k. No matter what anyone says, anywhere.
I am aware of this; Warhammer in general, 40k and fantasy, has no real 'protagonists' – they do however have named/well-known characters. These take 'lead' roles in games and other media like books about the warhammer universe. You see this all the time, and in 40k games, odds are if SM's are in the game, it will be from their 'perspective' and their named dudes will be 'leads' most the time. I was thinking of games with the statement above.
2). User friendly does not suggest inherent value, tactically or otherwise. If you play vanilla Space Marines, you're actually putting yourself at a disadvantage in many situations. I don't think I need to provide anecdotes, but for the sake of argument, if you didn't anticipate a lot of high-strength fire and brought your marines in the typical "two tacs in rhinos" loadout, you're gonna burn.
Ofc you will. Bad tactics and bad decisions will fuck you over, this is well known. My main reason to think of SM's as 'user-friendly' is, if you have for instance a Tau or Eldar or Dark Eldar force, these are factions with very specialized units. All of them have specific uses and usually don't do other things well, at all. Tau fire-warriors for instance, are excellent long-range but will evaporate if a headless toddler attacks them in melee – a SM tactical unit (last I looked atl, I'll admit it's a while ago now) can hold it's own in either of those, if they need to. I'm far more fond of forces where you HAVE to orchestrate all your forces perfectly to counter enemies with their strong points and avoid getting them tied up in situations where they will lose badly. SM's are far more forgiving on any slip-ups in this regard, and to me having a force where you must know exactly what your doing is far more rewarding to play.
3). There is no such thing as a perfect army. Ergo, even the vanilla SM player has to take at least an iota of strategic thought into account if he wants to make a useful army.
Yes, he does. Answer to point two answers this.
4). A manicured army doesn't ensure success. A vanilla SM player running into battle head-long against a DE army, or going toe-to-toe with an Ork hoard, has fucked up his tactics and will lose to a superior strategist. In fact, ALL armies will be rolled by a superior strategist in most circumstances, barring variables attributable to random luck or other unknowns.
Again, point 2. However it seems you have the impression that I said that SM's are entirely able to beat all others no matter what; I can't recall aiming to say something this dumb, because it's not true. Your statements here is mostly self-evident truth.
5). Just because you don't like the lore behind Space Marines, doesn't discredit it. I think Eldar are a ridiculous combination of overplayed elven aloofness and technobabble, doesn't mean someone else doesn't see value in it. Or as you put it, "we're entitled to our opinions."
I've no problem with the lore behind SM's, for the most part. I actually like Space Wolves for their awesome Viking/Werewolf tendencies – same reason I really, really don't like the silly vampire-like Blood Angels – and Ultramarines are somewhat cute. This is another conversation entirely however and these two chapters don't 'redeem' how horribly over-hyped and super-glorified SM's are in a general sense. For this reason, if I'd have to roll an Imperium-loyal force it will likely be SOB or IG. I'm not sure, to be entirely honest, why I like SOB more than IG – they have many similarities to SM's while IG are very different and far more heroic, again.
And before that, there are no less than 2 other factions ahead of them in the option's list, 5 if we include Warhammer fantasy.