No indication as to what they wrote and whether or not it is true or blatantly false as he claims. If the statements are demonstrably false, then I approve of his approach. If they are true then it looks like he is trying to intimidate them.
Apparently it is true ... true enough that Lamborn claims to have returned the donation (though there's apparently no record of that).
Lamborn knows he's in for a rough primary fight, and if he gets on the wrong side of Focus on the Family, he'll have some difficulties. He is a hothead, however ... and this remarkably stupid move is seriously bad news for his primary campaign.