What do you mean by "accepted him as a delegate"???Typically what happens is each campaign recruits delegates (or people apply to be delegates) after their state primary is held. These delegate applicants, if approved at the state convention, will to go the national GOP convention and cast a vote for their state for the GOP candidate that won that proportion of the state's votes. So, in this case, Tennessee, there are 33 Trump delegates, 16 Cruz delegates, 9 Rubio delegates.
The vetting process is done before (or during) the state convention. So this guy, who backs Trump, applied to be a delegate to party officials and was approved even though he stated his radical views to the Trump campaign. Therefore, the Trump campaign knew about this guy, but still accepted him as a delegate.
Does a candidate have any choice is returning delegates that they find unacceptable, after the state picks the guy? Is there a lemon law or return policy?