"It's not illegal to meet with someone to find out what they have to offer," Smith said.
Crucially, this email chain has a past and a future. How did it come to Rob Goldstone finding this Russian woman, how did he come into contact with her, how did he learn that she was affiliated with the Russian government, what was Rob Goldstone's relationship to Trump Jr, and the campaign in general... Basically, how did it come to this chain and this proposed meeting. The future, what did Manafort and Kushner have to say, what happened at the meeting, then afterward between the aforementioned individuals, largely reprising the questions. Normally this context is where the suspect would look or point to for relief.

But it's hard to imagine what information could put the situation in a better light, since what is revealed hints that certain notions about Russian activity may have already been accepted as a matter of course by highest levels of the campaign, and is already far beyond mere political shop talk. What do you expect a certain someone may or may not have to offer, and why do you expect it?

E.g. "Mr. Trump Jr. I recommend you meet this Russian woman, she has some good ideas on campaign strategies and avenues of attack on Clinton" vs. "Mr. Trump Jr. I recommend you meet this Russian woman peddling an intelligence package on Clinton with the alleged approval of the Putin regime.' Followed by recognition of the proposal and enthusiastic engagement.There are several analogies here, including corrupt money: advice on how to make money against direct discussion of pecuniary blandishments; and murder: talking about wanting to kill someone against taking premeditated action with the end of killing someone.