Jared Kushner’s interest in creating a back channel is not the problem. But the context is what makes the revelation so suspicious.
If it is true that Kushner considered setting up a back channel, it would have come after Russia intervened to help the winner in the election, as multiple intelligence agencies have affirmed it did. The back channel discussion would have taken form under a president-elect whose economic interests remain a mystery, including those in Russia.
It is difficult to separate the idea that Kushner was mulling such under-the-radar communication from a larger context in which numerous officials — in the Trump campaign, the transition team and administration — hid their contacts with Russians. Add all that up and the Trump White House has very little credibility to defend itself by saying there is nothing worthy of concern.