What do you mean by "hurting local businesses"? Wouldn't more highly paid workers in the area be good for local businesses?
That said, perhaps the fear is "over-cutting" -- that HQ2 slurps up top talent from local tech businesses and overbids salaries. I can totally see that happening, especially with the only-handful of truly high-tech businesses in the Northern Virginia community. This is a bad thing short term and a good thing long term.
It didn't revitalize that neighborhood like the city was hoping for.
If you give so much away, the tax benefits cease existing.