It has more to do with visibility then anything else. Indians have emerged as the “visible” minority group due to their number in the last few years in Austaralia (there are more then 200,000 Indians in Austarlia and just 20,000 Pakistanis !!! ) … hence the threat perception by white groups. This is similar to what happened in UK in the 60-70 era … that time Pakistani were the more “visible” minority group and had to bear the brunt of attacks from white groups.
The term “Paki bashing” was invented when white gangs used to thrash south asian (mainly Pakis) … guess the “stronger” Pakistanis did not make it to UK 