Was it that he voted against a bill in committee and voted for a watered down form of the bill? Too many people say JFK voted against Civil Rights in 1957 for this to be accepted as a falsehood.
(
@JonNC too) Look to authoritative sources, not popular news sources.
JFK votes against the Aiken-Anderson amendment, which would have weakened the bill. But he, along with all these senators voted for the bill:
Aiken (R-VT), Allott (R-CO) Barret (R-WY), Beall (DMD), Bennet (R-UT), Bible (D-NV) Bush (R-CT)
Carroll (D-CO), Case (R-NJ), Case (R-SD), Church (DID), Clark (D-PA), Cooper (R-KT), Cotton (R-NH),
Curtis (R-NE), Dirksen (R-IL), Douglas (D-IL),
Dworshak (R-ID), Flanders (R_VT) Frear (D-DE)
Goldwater (R-AZ), Hayden (D-AZ). Hennings (D-MO),
Hickenlooper (R-IW) Hruska (R-NE), Humphrey (DMIN), Ives (R-NY), Jackson (D-WA), Javits (R-NY),
Johnson (D-TX), Kefauver (D-TE), Kennedy (D-MA),
Knowland (R-CA), Kuchel (R-CA), Langer (R-ND),
Lausche (D-OH), Magnuson (D-WA), Martin (R-IW),
Martin (R-PA), McNamara (D-MI), Monroney (D-OK),
Mundt (R-SD), Neuberger (D-OR), O’Mahoney (D-WY),
Pastore (D-RI), Potter (R-MI), Purtell (R-CT),
Proxmire (D-WI) Revercomb (R-WV), Saltonstall (RMA), Schoeppel (R-KA), Smith (R-NJ) (Smith R-ME)
Symington (D-MO), Thye (R-MIN), Watkins (R-UT),
Wiley (R-WI), Williams (R-DE), Yarborough (D-TX),
Young (R-ND).
The following senators voted against the bill:
Byrd (D-VA), Eastland (D-MI), Ellender (D-LA),
Fulbright (D-AR), Hill (D-AL), Holland (D-FL),
Long (D-LA), McClellan (D-AR), Robertson (DVA), Russell (D-GA), Scott (D-NCS), Smathers
(D-FL) Stennis (D-MI), Talmadge (D-GA),
Thurmond (D-SC).
You can find this list
here and
here and
here. In the last reference, just hover your mouse over the state of Massachusetts.