This reveals a lot about Trump.  It's style over substance.  On nearly all substantial policy issues, Flake has been a consistent supporter, eg., on confirming Gorsuch and all Trump appointments; on Obamacare repeal, regulatory reform, and Flake will definitely and enthusiastically support tax reforms.  Flake just thinks Trump's unpresidential outbursts hurt the consevative cause and redefine the Republican Party in ways that don't have a winning future.  Flake is 100% right on this point.  Why other Republican leaders, who by the way think the same thing as Flake, don't speak up is a shame.  So Trump will offend the senate by trying to take out a firm policy ally, all so he doesn't have to be criticized?  What a "snowflake" Trump is.