Is killing infidels allowed in Hindu Scriptures?
No , killing of Infidels are not fully allowed in Vedas. There are some mantras in Atharva-Veda which asks god agni about destroying evil minds of foes , pardoning / Sheltering then , Welcoming those who came to ask pardon /shelter. Destroying only evil-nature or evil-mind of foes and not the people , even Atharva-Veda prays to god agni for welfare of son's and daughter's of evil-minded people and to motivate them towards good path.
Atharva-Veda , First Kandam , Sukta 7 & 8 , YatudhanNashan Sukta.
Atharva-Veda Samhita , Translated by Pandit ShriRam Sharma Acharya. Published by - Yuga Nirmaan Yojana , Mathura , Uttar-Pradesh , which is a hindi translation.
These are some of the mantras from Atharva-Veda.
पश्याम ते वीर्यम् जातवेदा प्र णो ब्रुहि यतुधानान नृचक्ष: ।
त्वया सर्वे परितप्ता: पुरस्तात त आ यन्तु प्रब्रुवाणा उपेदम ॥ 7.5॥
O Agni you are the form of the knowledge , let us see your bright bravery. You are the guide to whom who have lost the right way. By your grace lead our foes to the right path. By your order, let wickedness come here to repentance by identifying themselves.
अयं स्तुवान आगमदिमं स्म प्रति हर्यत ।
बृहस्पते वशे लब्ध्वाग्निषोमा वि विध्यतम् ॥ 8.2॥
Welcoming those wicked minded people who came here for repentance. O guiding star! source of bright knowladge! By your grace take them in your control. To cure them, O Agni & Soma examine them.
यातुधानस्य सोमप जहि प्रजां नयस्व च ।
नि स्तुवानस्य पातय परमक्षुतावरम् ॥8.3॥
O Soma! you let us drink the nectar of knowledge by your grace. Let the evil-nature gets destroyed by roots, let this reach to the children of evil-minded once & let them also be made good minded. Let the eyes be lowered of those, who praise you.
so from above shlokas of Atharva-Veda it is clear that vedas do not at all support/suggest the concept of infidels. It supports a Humanist approach towards enemies, evil-minded people.
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