Response:
One: reports indicate that tens of thousands of companions attended the announcement of Ghadir. Some reports state 70,000, while some state 120,000. Here the Sunni scholar Sibt ibn al-Jawzi states there were 120,000 with the Prophet:
قال سبط بن الجوزي الحنفي شمس الدين في (تذكرة خواص الأمة) اتفق علماء السير إن قصة الغدير كانت بعد رجوع النبي (صلى الله عليه وآله وسلم) في حجة الوداع في الثامن عشر من ذي الحجة جمع الصحابة وكانوا مئة وعشرين ألف وقال من كنت مولاه فعلي مولاه
So no, this was not some minor announcement for a few companions in Medina. It was a major announcement for the people of Medina and all those villages around Medina. So he wasn’t alone with the residents of Medina only. And remember that Ghadeer Khumm is closer to Mecca than Medina, and this in itself indicates the announcement was not only for the people of Medina.
Secondly, why delay the companions in the heat of the sun after Hajj (which is a difficult and tiring journey) to make this announcement? Couldn’t he just have waited to arrive Medina and say it there?
Two: Sunni sources documenting the hadith clearly indicate what the Prophet (s) meant by the word Mawla. He wasn’t talking about some skirmish in Yemen.
Look at the hadith narrated by Nisa’i:
وأخرج الحافظ النسائي في الخصائص : عن زيد بن أرقم قال : لما رجع النبي ( صلى الله عليه وآله وسلم ) من حجة الوداع ونزل غدير خم أمر بدوحات فقممن ثم قال : كأني دعيت فأجبت وإني تارك فيكم الثقلين ، أحدهما أعظم من الآخر ، كتاب الله وعترتي أهل بيتي ، فانظروا كيف تخلفوني فيهما ، فإنهما لن يفترقا حتى يردا علي الحوض . . . ثم قال : إن الله مولاي وأنا ولي كل مۆمن : ثم أخذ بيد علي ( رض ) فقال : من كنت وليه ، فهذا وليه ، اللهم وال من والاه وعاد من عاداه . . . فقلت لزيد : سمعته من رسول الله ( صلى الله عليه وآله وسلم ) قال : نعم ، وإنه ما كان في الدوحات أحد إلا ورآه بعينه وسمعه بأذنيه . . . )
The Prophet (s) says: I am about to depart soon. Then he says I leave behind me the Qur’an and my family of the Ahlulbayt, and the shall never separate. Then he says “Allah is my Mawla, and I am the Wali of every believer.” Then he said Whoever I am his wali Ali is his Wali. Just ask any unbiased and objective person to analyze this statement. Does it sound like he is talking about some skirmish in Yemen? It’s clear he is talking about religious authority: I am about to leave…hold on to Qur’an and Ahlulbayt, Allah is my Mawla…I am the Mawla of every believer…Ali is the Mawla. It’s very clear. So even if the word Mawla has many meanings, the context makes it clear.
Also, Dhakha’er al Oqbah by al-Tabari and Ahmad ibn Hambal in his Musnad state the Omar congratulated Ali after that and said:
هنيئا لك يا بن أبي طالب أصبحت وأمسيت مولى كل مۆمن ومۆمنة
We don’t need to prove there was a procession. Omar’s congratulatory statement makes it clear he was congratulating him on an important position, no that Ali is now a friend or a good pious Muslim.