Saw tweets from Periyarists claiming Saivites(Lord Shiva Devotees) are not Hindus. This is ridiculous and deceit to keep Hindus divided. There are 72 sects in Islam and several in Christianity. If you are an atheist better stay away from all religions.
Skanda Purana told by 1/n

2/n
Lord Muruga ( Tamil Name Kandan) talks extensively about Lord Venkateswara's history till marriage in the 1st chapter and 2nd chapter covers Lord Puri Jaganath's history.
Lord Muruga is Shiva's son. All Tamil saints have revered about Lord Venkateswara. Rishi Agastya

3/n
Was a direct Disciple of Lord Shiva, sent from Himalayas to South for spreading the Knowledge gained from Shiva. Agasthya is the top most Guru of Tamil Siddhas. The same Agastya teaches Aditya Hrudayam to Lord Rama in Ramayana to defeat Ravana. So Shiva and Vishnu are

4/n
2 of many branches of Sanatana Dharma. In Mahabharata Krishna takes Arjuna to Kailasa to get Divine Asthras from Shiva. So there is no proof in our Puranas that Shiva is not Hindu and only Tamil God. These Athiests should practice atheism without interfering in any religion