It is safe, but I wouldn't recommend it. It is always best to let your videos stand on their own and not use artificial metrics which could be detected and result in punishment and / or suspension of your account
This is an example of a google response...
https://productforums.google.com/forum/ ... xq4xg8eG4QAt the moment, we are implementing improvements that will prevent users from accruing higher counts of these metrics as a result of invalid activity.
YouTube employs proprietary technology to prevent the artificial inflation of a video’s viewcount, likes, and other engagement metrics by spam bots, malware and other means. These changes will improve the integrity of these engagement metrics by ensuring that these numbers accurately reflect user intentions. As such, if you notice an overall decrease in such activity with respect to your video and channels, this is due to better filtering of this activity from spammy sources.
Recently, we’ve seen a rise in creative agencies and vendors that claim to increase subscribers and/or views while complying with the YouTube Terms of Service. For most of these companies, those claims are false; the purchase or gaming of subscribers, views or any other engagement metric is a violation of our Terms of Service. If detected, it may have the opposite effect and hurt your campaign, because the behavior could result in the suspension of your account.