Salaam alaykum wa rahmatullah,
I admit that I have zero expertise in ahaadith but having studied for law school exam, I can spot flawed reasoning and the failure of premises to support a conclusion.
Having never heard of Shahr ibn Hawshab, I did some research and found out the following:
1. A Muslim posed a question to a scholar. Not getting into the details, we can deduce from the answer that Shahr ibn Hawshab's reports are acceptable
when corroborated by others.
Please visit:
https://www.islamweb.net/en/fatwa/371374/a-hadeeth-by-shahr-ibn-hawshab2. Also, tadlees is not a simple task. Please visit the following link to read about different types of tadlees, the ruling of a hadith with tadlees and the ruling of a person who practiced it:
https://islam.stackexchange.com/questions/46975/what-exactly-is-tadlees3. The very next line in the article by TwelverShia - "actually there is not a single authentic narration from any companion who considered the incident of Ghadeer to be the proof of Imamate and leadership of Ali (ra)" - loosely points to the my first point. What Shahr ibn Hawshab narrated is not corroborated by anyone else. However, the Rawaafidh are too busy reading their own meaning in something they do not understand so it is natural for them to lose track of supporting evidence.
Therefore, the "refutation" is not as simple as showing an authentic report by way of Shahr ibn Hawshab and claiming that he is a reliable narrator. Rather, the Rawaafidh will have to present an authentic report by way of Shahr ibn Hawshab not corroborated by anyone else or any other chain.