The rumors are true, Joe Manganiello will be playing Deathstroke in the Batman movie.
http://www.theverge.com/2016/9/8/128...roke-dc-comics

Deathstroke? Why him?

If these rumors are right then it actually makes sense why Deathstroke appears in the movie. But take these rumors with a grain of salt. Interesting that they managed to get Deathstroke's actor right.
http://bgr.com/2016/09/01/dc-extende...mors-spoilers/

Because people are tired of Joker, Jared Leto's Joker was godawful, Deathstroke is popular and because Deathstroke would be rather unique with the fight scenes

But Deathstroke is not really a Batman villain, he's a Titans villain.

How about doing Clayface? Oh wait, nope, can't do him, that would mean making it feel like a comic book and WB doesn't want that.

Okay then, what about Black Mask, Rupert Thorn, Scarface, and Penguin in a crime war? Nah, that would be too sophisticated and thought provoking.

Then there's Firefly, Man-Bat, Anarky, Mad Hatter, Professor Pyg, Onomatopeia, Sportsmaster, etc.

But yeah, I guess if they want to play it safe, Deathstroke makes the obvious choice.

Batman and Arrow have been stealing Deathstroke from Nightwing and Aresenal for quite a while now.

Clayface is a mook, he's not big enough to have a plot centered around solely him.

Firefly would have to be a double feature, Man-Bat would be too sympathetic and ignorant move-goers would just compare him to the Lizard, Pyg I could do without, Onomatopeia is an Arrow villain, so why would Bruce steal from the guy that literally rips him off in style anyway?

Sportmaster was only made cool in Young Justice, and then they were really pushing it.

Anarky could work, but DC would like run the risk of the mouthier fanbase just prefer him to Batman, and they can't have that.

Mad Hatter they could only put in if they have the mature skill and the balls to handle a creepy, slightly rapey villain like him. Because if and when they fuck that up it's going to be a shitstorm they can't recover from.

Meanwhile Arrow used Deathstroke and people LOVED it, not to mention Deathstroke got lots of popularity in the Arkham games
Like previously stated, Clayface is not main villain material, not to mention it'd have an unnecessary amount of CGI in the fight scenes
Too many characters to introduce in a single movie, meaning it'd be a clusterfuck
Out of the examples I know, Mad Hatter's the only one who's got potential as a main villain as Firefly's a mere arsonist and Man-Bat's just kinda there
Deathstroke's also got lots of potential for a stealth fight with Batman, not to mention Batsy would probably go after a serial killer who sees it as his job than other loonies

I honestly think Firefly could work as a main villain. He's fucking iron man with a flame thrower.
They just have to change him from a mook who has the same mindset as Flame Hyenard.

Honestly I'd say Deathstroke is sort of a more of a general 'DC comics' bad guy than a specific member of a rogue's gallery, at least in recent years. Plus, he's a mercenary, having him be hired to go after Bats is pretty dang easy to justify.

Plus, if the rumors posted up above are true, we'll be getting way more bad guys than just him. So, maybe calm down a bit until we know more about the movie than "It's a Batman movie and Slade is in it."

I wanted Ron Perlman for Deathstroke in the movie, but I guess WB wants someone who is younger to appeal to kids and teens. I mean Ron Perlman does the voice and he can act too. Slade is like in his 50's or 60's from what I can remember, so it can work.