You can disagree with someone and still defend their right to their seat at the table.

Agreeing with someone and thinking they belong in the conversation are two different judgements. Once you start deciding who gets to speak based on whether they are right, you have handed somebody else that same power over you. Most groups drift this way slowly, by leaving one person off the invite rather than by any announcement. The cost shows up later, when nobody says the unpopular thing anymore.

Notice who in your class or your group has quietly stopped being asked. Ask what they think about something, out loud, in front of other people. You can argue with the answer once it is on the table.