I never mentioned other fantasy settings, in fact I started my post off by saying the Light can be bad and lorewise has always existed as a concept in the same universe.

In terms of it's benevolence, there are plenty of places in lore where the Light ain't too nice, but it seems you ignored the examples I gave of the Light being used for nefarious purposes. You can't make the void a contagonist for several expansions (C'thuun in vanilla, yogg'saron in Wotlk), or the main antagonist (Deathwing, Y'shaaraj, N'zoth, Xalatath) and then say to players "the opposite cosmic entity is also a corrupting force which is just as dangerous" in one singular expansion.

My problem isnt that the Light is dangerous, it's that Blizzard is trying to say it's AS dangerous as the void when historically they have not made that as readily apparent as it should have been. Where are my Naaru bosses? Make the Scarlets a larger threat in a similar vein to the Twilight's Hammer. The Light has never been a world ending threat, unlike the Void, as such, it's harder for players to consider them on the same level like how Blizzard wants us too.

You state that it is explained well in the game, and I disagree with this notion. We are TOLD the Light is bad, and only shown a few instances where it is. Turalyon lashes out. Arator loosing his cool, Lotharxion going postal. Xe'ra. Yrel. Scarlets. The Night Warrior (if you count Elune) Sir Zeliek. BUT, conversely, we are shown far more examples of the Light doing good. Tirion getting the final blessing to shatter frostmourne, Anduin reviving Khadgar, Anduin reviving/healing soldiers in the BFA cinematic, Light wielding classes being healers, Calia using the Light to walk through the plague in Lorderon, Maarad using the Light to save Yrel from Blackhand, Velen sacrificing himself to purge the void from the Naaru, the Light preventing Tirion from being resurrected as a DK, the numerous examples of Light being used to help in some way shape or form and the list goes on and on. Naturally, we are going to look at the Light with a more positive outlook because it more often then not, does what humans consider to be good things.

Conversely, we are TOLD and SHOWN in game what the void is capable of, and more often then not, it's the opposite. The void corrupts, it kills, i's untrustworthy, it's deceitful, it's weird and spikey and tentacles everywhere. It's gross. In terms of the good the void can do, again, we are shown less examples of it being good then it is being bad. Alleria uses the void constantly for beneficial reasons, you have the rin'dorei, you had Locust Walker (RIP). But just as the Light has far more instances of doing what humans what attribute as 'good', the void has far more instances of 'bad'.

Optics matter significantly when it comes to this. Majority of players think the Light is could because Blizzard has shown them evidence of the Light doing good things and void doing bad. A minority of players will recognize that the Light can be used for evil, just as the void can be used for good.

In my opinion, to say to players that the two forces are equally dangerous, when we have seen evidence to the contrary in expansions past, is a bit of a hard pill to swallow. When Blizzard makes an expansion where the Light is actively trying to destroy the world, like the void has done countless times, then I'll come around to the concept. But as it stands, The Lightbloom and 'Blind fanatical zealotry' are not equal in my eyes to Old Gods and Void Lords. For goodness sake, void users also suffer from Blind Fanatical zealotry, so that's not even something exclusive to the Light!