ACR X TCASII RA WITH VFR C172 REFUSED CLRNC RADAR VECTOR HDG. NONSTANDARD USE OF TCASII EVASIVE ACTION TURN.

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I WAS VECTORING ACR X; A B737; FOR A L BASE ENTRY FOR A VISUAL APCH TO RWY 35. X WAS RESTR TO 3000 FT DUE TO PA23 TFC AT 2500 FT SE OF X INBOUND FOR RWY 6. TA'S WERE EXCHANGED BTWN THE 2 ACFT. X WAS ASSIGNED A 090 DEG HDG STILL AT 3000 FT. X ADVISED HE WAS DEVIATING TO THE R; REFUSED THE HDG DUE TO A TCASII ADVISORY. CLOSEST TFC WAS THE PA23 STILL INDICATING 2500 FT. X SAID HE SHOWED SOMETHING DIFFERENT. THERE WERE 2 OTHER ACFT 4-5 MI FROM X; ALL WERE SEPARATED BY 1000 FT. CONTINUED TO ADVISE ME OF HIS TCASII TA'S ON THE FREQ. ACR X DECISION TO DEVIATE LATERALLY BASED OF TCASII INFO WAS TOTALLY UNEXPECTED. HIS ACTION CAUSED ME TO CHANGE MY ARR SEQUENCE. X APPARENT CONCERN WITH TCASII ADVISORIES MADE ME CONCERNED THAT HE WOULD DEVIATE AGAIN WITH THE NUMBER OF ACFT UNDER MY CTL; SAFETY WAS COMPROMISED BECAUSE OF ALL THE ATTN AND DISTRS CREATED BY 1 ACFT FOCUSING IN ON TCASII. THIS IS MY SECOND EXPERIENCE WITH A TCASII ACFT DEVIATING LATERALLY BASED ON A TCASII ADVISORY. (PREVIOUS OCCURRENCE; AN ATR42 TURNED TO AVOID A TARGET 500 FT BELOW. THE PLT ADVISED IT WAS NOT AN RA BUT A TA.) THIS APPEARS TO BE BECOMING A DANGEROUS TREND.