What's so baiting in Benoit's words to Linda?

If I remember correctly, this is the scene where Blanc interviews every member of the family, which serves both as a general introduction for the viewer and the start of the investigation.

During each interview, Blanc was trying to get the suspects to reveal hints and suspicions, and I think that's what he's doing here: by trying to depict Walt in a more positive light than Linda, he may want to trigger her into badmouthing Walt, potentially revealing a motive for the murder.

Linda elaborates in the rest of her line

LINDA: Are you baiting me, Detective? You know he doesn't, and you think I'm dumb enough to be baited into talking family business, into shit talking my brother in front of a police detective and a state trooper -

As mentioned by @MichaelSeifert, Richard does get baited and explains that Harlan doesn't want any of the things Benoit mentioned:

RICHARD: Walt doesn't run shit! There are no film or TV rights, Harlan's never allowed any adaptations of his books. Hates the idea.

BLANC: No!

RICHARD: Oh yeah! Drives Walt nuts, cause that's where the real money's at. When he gets a little Irish courage in him he'll get into it with Harlan.

BLANC: Did he get "into it" at the party?

RICHARD: Oh my god. He wouldn't leave him alone, poor guy. Harlan had to give him the hook.

The "hook" Richard mentions is Harlan hooking his arm into Walt's and pulling him into a room to discuss something.

Presumably, Benoit has done some research and is aware that Harlan is against the idea of merchandising, adaptations, film and television rights. The fact that he specifically mentions those things is what's baiting about his question.

Benoit is also aware of a screaming match Harlan had with someone in the morning.

BLANC: You see, I spoke with the caterer this morning. She didn't see you helping her staff, but she did hear Harlan in a screaming match with someone that afternoon. In his study.

RICHARD: I don't, a screaming match? No. Joni was here too, she was early, maybe it was her, ask her.

BLANC: These were two male voices.

Linda was the first to be interviewed, so Benoit wouldn't have been aware of Richard's comments at the time. It makes sense that he was probing for who might have been involved in that shouting match, or any other potential motives that Linda might reveal in an emotional outburst.