According to wikipedia:
Anti-Hinduism is a negative perception or religious intolerance against the practice and practitioners of Hinduism.
So, it is simply about against practices and practitioners of Hinduism. Now if you think Hinduism is Dharma, then anti-Hinduism is simply Adharma.
From Srimad Bhagavat Purana 7.15.12:
विधर्मः परधर्मश्च आभास उपमा छलः।
अधर्मशाखाः पञ्चेमा धर्मज्ञोऽधर्मवत्त्यजेत् ॥
There are five branches of irreligion, appropriately known as irreligion [vidharma], religious principles for which one is unfit [para-dharma], pretentious religion [ābhāsa], analogical religion [upadharma] and cheating religion [chala-dharma]. One who is aware of real religious life must abandon these five as irreligious.
So, if you need such tag you can use tag adarma. (or dharma may also work)
I think we should not use/allow tag anti-hinduism.
In fact I think anti-hinduism is modern idea and is not
on-topic or in our scope of this site. Example, this question was (before deletion) closed as off-topic:
This question does not appear to be about Hindu religion, within the scope defined in the help center.
There are currently two question in our site (I've corrected/fixed one where this tag is used incorrectly I think) tagged to anti-hinduism:
- Wendy Doniger and the Bhagavad Gita
- Do Hindu texts talk about how to respond to ideology which is against Hinduism?
The first one is closed as primarily opinion based which I think off-topic also. And the second one is only surviving for this tag which can be answered from Dharma-Shahtra I think but we don't need anti-hinduism.