Due to the various Linked-In scams, my policy has been to ignore all invitations. I received one that appeared to be from a man I know, but when I contacted him, he said he hadn't sent it. The ways of the scammers are as multifarious as they are devious, so to save time I delete first and ask questions later.
What may appear to be rudeness is really just caution. It is in the nature of the consevative to be cautious, as it is in the nature of the leftist to be reckless and foolish and to make a mess of things. Example: Obamacare.