If you see a thin, glowing blue line coming at you from an allied Cruiser (and sometimes Sci, or even an Escort), don't run from it! It's not scary!
If you look closely, when you're within 7.5KM, you'll see that there's actually a secondary ring around your shields.
Your ally is using Extend Shields on you, greatly improving your shield resistance and healing your shields which will help you survive longer. If nothing else, respect that your ally is trying to keep you alive and that by giving you Extend, they're freeing up other heals to go to other teammates. Don't run out of range!
tl;dr - Stop freaking running away when I freaking Extend you and expect me to chase you down across half the map to heal you.
More specifically, it's because the extend shields animation is identical to the tachyon beam animation, right down to the rippling against your shields part. Make the tachyon mean yellow or something.