I think when several factors, all of which are perfectly arguable points for debate, are met. Personally, off the top of my head, I can think of these criteria (warning, pedantry forthcoming!):
When the majority of a group are of a particular bent (lets just use racists as the example) are racist and express it openly
When the majority of a group are racists but don’t express it openly
When a plurality of a group are racist and open/are racist but don’t express it openly
When an influential minority of a group are racist and open/are racist but don’t express it
When the leadership that dictates group policy are racist and open/are racist but don’t express it
When some important faction of the group that needs to be placated and catered to in order for the group as a whole to achieve their goals are racist and open/are racist but don’t express it
More debatable are those opposing the racists. The above assumes the non-racists are passive, there are also varying debatable points when there is a voice actively opposing the racists.
If you take the above and add an opposing and equal voice, then its far more difficult to slander the whole group as racist. The debate, at least for me, then comes down to the success, influence, and/or vehemence of that opposing group.
Of course, another delineation point can be where we are talking broadly about the group or about an individual within the group, or a small subsection of the whole group. In lance’s example, JFK may or may not be a racist when the Democratic party as a whole are racists, his character is defined by himself only since we are only talking about him. Humans are capable of making the transition between speaking broadly or narrowly, lance, and that’s the point I think you miss often.
With the case of the GOP, I agree with many that they are a racist organization. They fit several of criteria above. Their leadership has said horribly racist things, supported racist things, and they have a faction of varying size that has been very racist in its public sentiments. They have racist pundits, influential individuals, vocal minorities, you name it. And I do not see a significant push by opposing voices in their party to shut those racists down. Factually, I think, the GOP can be described as racist. Individually, maybe there are non-racists that outnumber the racists, but they are certainly keeping quiet and don’t make waves. Where are the moderate Republicans anymore? Quitting the party, changing parties, or getting out of politics.
Lance, if you want to claim everyone’s the same, then you come up with a set of criteria which you think can be used to define a group, I’ve given mine already