"Is objectively dangerous"=/= "meriting a different treatment". Besides, the people who can subdue and police/hunt down the people who light people on fire with their mind are objectively more powerful than them, otherwise they wouldn't be able to do that. Want to lock those up? Who will do that? And then you'd have to lock up the new people too, because they'd be even more powerful and dangerous. And so on. Bullshit.
Also, your second would only make sense if laws were never idiotic or unfair. Is this what you're arguing? That everything that's legal is always good? Because if you're not doing that, you can't use legality as a basis for what is acceptable and what isn't.
Soldiers undergo extensive training and screening process, their abilities are not given randomly to the Hannibal Lecters of the world like magic is.
And then, Templars are especially dangerous to mages because they disrupt mana, not so much to normal people.
Then, their weapons can be taken from them.
Then, they aren't susceptible to possession except in very special cases.
Then, non-mages who, without Templar abilities, can match and defeat mages are above the norm whereas the average mage is more dangerous than the average normal person.
It's not "laws". It's the very concept of the legal system, restrict our freedoms so we can coexist.
People in our world and Thedas live under this. Should mages be the exception?
But "we just want equal rights under the law", you'll say. And I'll say, the mages aren't equal. The fact they are more dangerous means their restrictions must be harsher to account for this, it's only logical and fair.
And then you'll refuse this because you've done so in the past.