A junior partner at a law, on the verge of a promotion, must represent his estranged mother, a social activist accused of inciting a peaceful protest turned violent, in a high-profile pro-bono case to salvage the firm’s reputation.

What do you all think about this logline? / the general idea of the story?

First of all, welcome! Glad you chose to post your idea here on SS!  Anyone here can tell you I can’t resist a good logline challenge, so what about something like:

***When a social activist is accused of inciting a violent protest, her estranged son is slated to lead her pro bono defense in a move fashioned to salvage his law firm’s reputation. ***

Think of your logline as the teaser, then flesh out the details (her belief the protest was to be peaceful, his lack of legal experience, back room deals at the law firm, etc.) in your script.

Good luck with this. I like the premise and feel it could be a very compelling story. I hope you will consider posting your finished draft here.  

A junior partner at a law firm (I assume)?
I would say that's a conflict of interest, but in a screenplay conflict is what you want, so all good there..

Your logline is fine but it doesn't exactly excite me.
And it brings up a lot of questions.

The stakes appear to be the lawyer's promotion and the firm's reputation? Why should we care if he gets a promotion? Why does the firm need to re-establish it's reputation and why do we care about it as well?

Pro-bono, so no money coming to the firm.

As for the main plot, I think you need to reveal more of it - what happened with the peaceful protest turning violent? What charges is she facing?

At the moment it doesn't attract me that much cause I'm not getting the real crux of the story.

Look at The Firm, The Client, The Lincoln Laywer, The Judge, Presumed Innocent, A Time to Kill, To Kill a Mockingbird etc., - the stakes in these movies are high - they deal with murder, seduction, infidelity, money laundering, racism, the mafia, and running for your life, or to save your life or someone else's basically.

So, at the moment I think your logline doesn't reveal enough and is too sedate.

An audience needs more to pick this off the shelf.