NL 100 - Overpair KK against bad TAG - He donks me

[YKMM]

Villain is a 21/4/2.5 in 100 hands as too passive preflop, I did not see him play badly postflop. I really hate folding (or even calling) here but I am WAY behind when faced against the range KK-AA, AdKd. Do I make a fold here or am I reading way too much into his donk bet (which it in itself a rare occurence at NL100)?

PokerStars No-Limit Hold'em, $1.00 BB (9 handed) Poker Stars Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

CO ($73.85)
Button ($77.75)
SB ($199.05)
BB ($20)
UTG ($89.15)
UTG+1 ($161.25)
MP1 ($102.05)
Hero ($88.10)
MP3 ($18.50)

Preflop: Hero is MP2 with K[img]/images/graemlins/diamond.gif[/img], K[img]/images/graemlins/spade.gif[/img].
UTG calls $1, <font color="#CC3333">UTG+1 raises to $4</font>, <font color="#666666">1 fold</font>, <font color="#CC3333">Hero raises to $15</font>, <font color="#666666">5 folds</font>, UTG folds, UTG+1 calls $11.

Flop: ($32.50) 4[img]/images/graemlins/diamond.gif[/img], Q[img]/images/graemlins/club.gif[/img], 5[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">UTG+1 bets $18</font>, Hero ......