They appear to be legit law firms.
Checked a few webpages and looked for inconsistencies in the site.
O'Neil, Cannon, Hollman, DeJong & Laing
Are in Wisconsin and appear this type of suit appears to be in their wheelhouse.
They appear to also "owned" the URL's below.
http://www.whois.com/whois/hpagediscriminationinvestigation.com
http://www.whois.com/whois/hpagediscrimination.com
Used Findlaw.com to lookup the lawyer and that also appears to be legit.
Appears so... at least to me. Proceed with normal due diligence.