Cana anyone recommend a plastic wrench that doesn'e scratch the metal?

Hand tight is fine. For a bit tighter a wide rubber band will greatly increase grip and leverage. If your binding posts are poorly designed or you're really determined to overtighten then tape your metal wrench. Sorry but people who overtighten are a pet peeve of mine. Don't be that guy. Please.

Over-tightening could potentially cause a problem when you go to remove the spades.  Binding posts are typically mounted to the cabinet/plate using a nut on the backside.  If the spades are too tight, it could cause the back-nut to loosen and then you are stuck with a rotating binding posts with spades that are locked on.

I wrap some blue tape over the ends of a wrench but as millercarbon stated DO NOT overtighten!

Once you know what size you need go on line to Snap-On and order the appropriate sized open ended wrench. Their wrenches are entirely polished and chromed. They will not scratch anything. Just be prepared to spend a bit more on them.  

Thanks for all the suggestion... I guess I'll just have to tape it over before tighten the post.

As long as you have the correct size socket, any type would do. You just don’t want it to slip, that will cause scratching. Put the correct socket on the post and tighten with your hand, no need for a ratchet. AudioQuest has made this.

https://www.amazon.com/AudioQuest-binding-post-wrench-Discontinued/dp/B0009XQUAM/ref=sr_1_1?hvadid=77996669303746&hvbmt=be&hvdev=c&hvqmt=e&keywords=audioquest+wrench&qid=1575396695&sr=8-1

@dill that was the one I was looking at but the inside looks like metal?

It won't matter, if you have the correct size, it won't slip so it won't scratch.
Any socket will do, you just need the correct size. I used a socket many times.

@dill thanks!

Hand tight is fine.
If you have trouble with the connector holding, you may need softer connectors/spring loaded styles.

Very hard spades don't grip well.

The Audioquest wrench will allow adequate tightening with little scratching.  Used with my VAC power amp for years and the Cardas binding posts continued to look good.

Try making one out of a small block of maple, pear or cherry wood. It’s also a great conversation piece.

This is why I think Furutech torque guard binding posts are the Best available. Impossible to over tighten, and silly easy to tighten properly. No tools required 

@zavato agree but seems an overkill solution to change the binding post completely for not wanting to scratch it lol

I get that but just commenting that they really are that good 

@zavato I agree with you though... speaker/amp manufactures should consider definitely consider thus option.

GOT IT!

Check out Knipex, German manufacturer of  (?) toolifile  tools for freak tool users. I got a beautifully German pair of channel-locks that came with a pair of synthetic “dentures” that snap onto the jaws. I use it to hold gold-plated connectors while doing the real torqueing from behind the face/back plate. I think they were about $25.
We’re audiophiles, man, we don’t need no stinkin’ cheap tools!

I’ll check into that @denverfred thanks!

@denverfred - do you happen to recall what model it is from the Knipex tools?  I searched on their website but can't seem to find the one you described.  Appreciate if you could let us know.

oh wow... @joecasey this is what I am looking for!  thanks a bunch man!

@rogerhifi, tools delivered today.   Bought the 4 SAE and 5 Metric sets.  7/16 fits my amp speaker connectors.

@joecasey I got the same set too!

Google soft grip pliers and buy on Amazon. They work and will not do any damage to metal parts.